[flang] Move runtime API headers to flang/include/flang/Runtime

This commit cherry-picks the change that Peter made in llvm-project and
makes additional changes to account for the differences between fir-dev
and llvm-project.

Here's the original message from Peter's change in Phabricator in
llvm-project:

Move the closure of the subset of flang/runtime/*.h header files that
are referenced by source files outside flang/runtime (apart from unit tests)
into a new directory (flang/include/flang/Runtime) so that relative
include paths into ../runtime need not be used.

flang/runtime/pgmath.h.inc is moved to flang/include/flang/Evaluate;
it's not used by the runtime.

Differential Revision: https://reviews.llvm.org/D109107

Author: klausler

flang/docs/tutorials/addingIntrinsics.md

@@ -342,7 +342,7 @@ void fir::runtime::genTrim(fir::FirOpBuilder &builder,
 The key point is `getRuntimeFunc<mkRTKey(Trim)>(loc, builder)` that builds the FIR signature for the runtime
 function automatically. The name passed to `mkRTKey` must be the same as the one inside `RTNAME` when declaring
 the function in the runtime headers. The runtime header must be included in the current file to use `getRuntimeFunc<>`
-(note the `#include "../../runtime/character.h"` at the top of the file). So at least the runtime API must be designed before adding
+(note the `#include "flang/Runtime/character.h"` at the top of the file). So at least the runtime API must be designed before adding
 the support in lowering.
 
 Then, the source file name and line number are lowered from the current location so that they can be passed to the runtime.

flang/runtime/pgmath.h.inc renamed to flang/include/flang/Evaluate/pgmath.h.inc

@@ -1,4 +1,4 @@
-//===-- runtime/pgmath.h.inc -------------------------------===//
+//===-- include/flang/Evaluate/pgmath.h.inc -------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.

flang/runtime/allocatable.h renamed to flang/include/flang/Runtime/allocatable.h

@@ -1,4 +1,4 @@
-//===-- runtime/allocatable.h -----------------------------------*- C++ -*-===//
+//===-- include/flang/Runtime/allocatable.h ---------------------*- C++ -*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
@@ -11,8 +11,8 @@
 #ifndef FORTRAN_RUNTIME_ALLOCATABLE_H_
 #define FORTRAN_RUNTIME_ALLOCATABLE_H_
 
-#include "descriptor.h"
-#include "entry-names.h"
+#include "flang/Runtime/descriptor.h"
+#include "flang/Runtime/entry-names.h"
 
 namespace Fortran::runtime {
 

flang/runtime/assign.h renamed to flang/include/flang/Runtime/assign.h

@@ -1,4 +1,4 @@
-//===-- runtime/assign.h --------------------------------------------------===//
+//===-- include/flang/Runtime/assign.h --------------------------*- C++ -*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
@@ -20,10 +20,10 @@
 // need not be handled here in the runtime; ditto for type conversions on
 // intrinsic assignments.
 
-#ifndef FLANG_RUNTIME_ASSIGN_H_
-#define FLANG_RUNTIME_ASSIGN_H_
+#ifndef FORTRAN_RUNTIME_ASSIGN_H_
+#define FORTRAN_RUNTIME_ASSIGN_H_
 
-#include "entry-names.h"
+#include "flang/Runtime/entry-names.h"
 
 namespace Fortran::runtime {
 class Descriptor;
@@ -42,4 +42,4 @@ void RTNAME(Assign)(Descriptor &to, const Descriptor &from,
     const char *sourceFile = nullptr, int sourceLine = 0);
 } // extern "C"
 } // namespace Fortran::runtime
-#endif // FLANG_RUNTIME_ASSIGN_H_
+#endif // FORTRAN_RUNTIME_ASSIGN_H_

flang/runtime/c-or-cpp.h renamed to flang/include/flang/Runtime/c-or-cpp.h

@@ -1,4 +1,4 @@
-//===-- runtime/c-or-cpp.h --------------------------------------*- C++ -*-===//
+//===-- include/flang/Runtime/c-or-cpp.h ------------------------*- C++ -*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.

flang/runtime/character.h renamed to flang/include/flang/Runtime/character.h

@@ -1,4 +1,4 @@
-//===-- runtime/character.h -------------------------------------*- C++ -*-===//
+//===-- include/flang/Runtime/character.h -----------------------*- C++ -*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
@@ -11,7 +11,7 @@
 
 #ifndef FORTRAN_RUNTIME_CHARACTER_H_
 #define FORTRAN_RUNTIME_CHARACTER_H_
-#include "entry-names.h"
+#include "flang/Runtime/entry-names.h"
 #include <cstddef>
 
 namespace Fortran::runtime {

flang/runtime/command.h renamed to flang/include/flang/Runtime/command.h

@@ -1,4 +1,4 @@
-//===-- runtime/command.h ---------------------------------------*- C++ -*-===//
+//===-- include/flang/Runtime/command.h -------------------------*- C++ -*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
@@ -9,8 +9,8 @@
 #ifndef FORTRAN_RUNTIME_COMMAND_H_
 #define FORTRAN_RUNTIME_COMMAND_H_
 
-#include "cpp-type.h"
-#include "entry-names.h"
+#include "flang/Runtime/cpp-type.h"
+#include "flang/Runtime/entry-names.h"
 
 namespace Fortran::runtime {
 class Descriptor;

flang/runtime/cpp-type.h renamed to flang/include/flang/Runtime/cpp-type.h

@@ -1,4 +1,4 @@
-//===-- runtime/cpp-type.h --------------------------------------*- C++ -*-===//
+//===-- include/flang/Runtime/cpp-type.h ------------------------*- C++ -*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.

flang/runtime/derived-api.h renamed to flang/include/flang/Runtime/derived-api.h

@@ -1,4 +1,4 @@
-//===-- runtime/derived-api.h ---------------------------------------------===//
+//===-- include/flang/Runtime/derived-api.h ---------------------*- C++ -*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
@@ -12,10 +12,10 @@
 // local variables.  Whole allocatable assignment should use AllocatableAssign()
 // instead of this Assign().
 
-#ifndef FLANG_RUNTIME_DERIVED_API_H_
-#define FLANG_RUNTIME_DERIVED_API_H_
+#ifndef FORTRAN_RUNTIME_DERIVED_API_H_
+#define FORTRAN_RUNTIME_DERIVED_API_H_
 
-#include "entry-names.h"
+#include "flang/Runtime/entry-names.h"
 
 namespace Fortran::runtime {
 class Descriptor;
@@ -40,4 +40,4 @@ void RTNAME(Assign)(const Descriptor &, const Descriptor &,
 
 } // extern "C"
 } // namespace Fortran::runtime
-#endif // FLANG_RUNTIME_DERIVED_API_H_
+#endif // FORTRAN_RUNTIME_DERIVED_API_H_

flang/runtime/descriptor.h renamed to flang/include/flang/Runtime/descriptor.h

@@ -1,4 +1,4 @@
-//===-- runtime/descriptor.h ------------------------------------*- C++ -*-===//
+//===-- include/flang/Runtime/descriptor.h ----------------------*- C++ -*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
@@ -18,9 +18,9 @@
 // User C code is welcome to depend on that ISO_Fortran_binding.h file,
 // but should never reference this internal header.
 
-#include "memory.h"
-#include "type-code.h"
 #include "flang/ISO_Fortran_binding.h"
+#include "flang/Runtime/memory.h"
+#include "flang/Runtime/type-code.h"
 #include <cassert>
 #include <cinttypes>
 #include <cstddef>