[clang][Interp][NFC] Add Dump debug op

This is often useful for debugging and dumps the current stack
contents.

Author: tbaederr

clang/lib/AST/Interp/Interp.h

@@ -1333,6 +1333,11 @@ inline bool FinishInit(InterpState &S, CodePtr OpPC) {
   return true;
 }
 
+inline bool Dump(InterpState &S, CodePtr OpPC) {
+  S.Stk.dump();
+  return true;
+}
+
 inline bool VirtBaseHelper(InterpState &S, CodePtr OpPC, const RecordDecl *Decl,
                            const Pointer &Ptr) {
   Pointer Base = Ptr;

clang/lib/AST/Interp/Opcodes.td

@@ -723,3 +723,8 @@ def CheckNonNullArg : Opcode {
 }
 
 def Memcpy : Opcode;
+
+//===----------------------------------------------------------------------===//
+// Debugging.
+//===----------------------------------------------------------------------===//
+def Dump : Opcode;