Cleanup header dependencies in LLVMCore

Based on the output of include-what-you-use.

This is a big chunk of changes. It is very likely to break downstream code
unless they took a lot of care in avoiding hidden ehader dependencies, something
the LLVM codebase doesn't do that well :-/

I've tried to summarize the biggest change below:

- llvm/include/llvm-c/Core.h: no longer includes llvm-c/ErrorHandling.h
- llvm/IR/DIBuilder.h no longer includes llvm/IR/DebugInfo.h
- llvm/IR/IRBuilder.h no longer includes llvm/IR/IntrinsicInst.h
- llvm/IR/LLVMRemarkStreamer.h no longer includes llvm/Support/ToolOutputFile.h
- llvm/IR/LegacyPassManager.h no longer include llvm/Pass.h
- llvm/IR/Type.h no longer includes llvm/ADT/SmallPtrSet.h
- llvm/IR/PassManager.h no longer includes llvm/Pass.h nor llvm/Support/Debug.h

And the usual count of preprocessed lines:
$ clang++ -E  -Iinclude -I../llvm/include ../llvm/lib/IR/*.cpp -std=c++14 -fno-rtti -fno-exceptions | wc -l
before: 6400831
after:  6189948

200k lines less to process is no that bad ;-)

Discourse thread on the topic: https://llvm.discourse.group/t/include-what-you-use-include-cleanup

Differential Revision: https://reviews.llvm.org/D118652

Author: serge-sans-paille

clang/lib/CodeGen/CGStmtOpenMP.cpp

@@ -30,6 +30,7 @@
 #include "llvm/IR/Constants.h"
 #include "llvm/IR/DebugInfoMetadata.h"
 #include "llvm/IR/Instructions.h"
+#include "llvm/IR/IntrinsicInst.h"
 #include "llvm/IR/Metadata.h"
 #include "llvm/Support/AtomicOrdering.h"
 using namespace clang;

llvm/examples/IRTransforms/InitializePasses.h

@@ -11,6 +11,7 @@
 #define LLVM_EXAMPLES_IRTRANSFORMS_INITIALIZEPASSES__H
 
 #include "llvm/IR/PassManager.h"
+#include "llvm/PassRegistry.h"
 
 namespace llvm {
 

llvm/include/llvm-c/Core.h

@@ -16,7 +16,6 @@
 #define LLVM_C_CORE_H
 
 #include "llvm-c/Deprecated.h"
-#include "llvm-c/ErrorHandling.h"
 #include "llvm-c/ExternC.h"
 #include "llvm-c/Types.h"
 

llvm/include/llvm-c/DebugInfo.h

@@ -16,8 +16,8 @@
 #ifndef LLVM_C_DEBUGINFO_H
 #define LLVM_C_DEBUGINFO_H
 
-#include "llvm-c/Core.h"
 #include "llvm-c/ExternC.h"
+#include "llvm-c/Types.h"
 
 LLVM_C_EXTERN_C_BEGIN
 

llvm/include/llvm/Analysis/AliasAnalysisEvaluator.h

@@ -26,6 +26,7 @@
 
 #include "llvm/IR/Function.h"
 #include "llvm/IR/PassManager.h"
+#include "llvm/Pass.h"
 
 namespace llvm {
 class AAResults;

llvm/include/llvm/Analysis/CycleAnalysis.h

@@ -18,6 +18,7 @@
 #include "llvm/ADT/GenericCycleInfo.h"
 #include "llvm/IR/PassManager.h"
 #include "llvm/IR/SSAContext.h"
+#include "llvm/Pass.h"
 
 namespace llvm {
 extern template class GenericCycleInfo<SSAContext>;

llvm/include/llvm/Analysis/MLInlineAdvisor.h

@@ -15,6 +15,7 @@
 #include "llvm/IR/PassManager.h"
 
 #include <deque>
+#include <map>
 #include <memory>
 
 namespace llvm {

llvm/include/llvm/Analysis/MemoryDependenceAnalysis.h

@@ -23,6 +23,7 @@
 #include "llvm/IR/PassManager.h"
 #include "llvm/IR/PredIteratorCache.h"
 #include "llvm/IR/ValueHandle.h"
+#include "llvm/Pass.h"
 
 namespace llvm {
 

llvm/include/llvm/Analysis/SparsePropagation.h

@@ -14,6 +14,7 @@
 #ifndef LLVM_ANALYSIS_SPARSEPROPAGATION_H
 #define LLVM_ANALYSIS_SPARSEPROPAGATION_H
 
+#include "llvm/ADT/SmallPtrSet.h"
 #include "llvm/IR/Instructions.h"
 #include "llvm/Support/Debug.h"
 #include <set>

llvm/include/llvm/CodeGen/ReplaceWithVeclib.h

@@ -16,6 +16,7 @@
 
 #include "llvm/IR/PassManager.h"
 #include "llvm/InitializePasses.h"
+#include "llvm/Pass.h"
 
 namespace llvm {
 struct ReplaceWithVeclib : public PassInfoMixin<ReplaceWithVeclib> {