Factor some of the constants+context related code out into a separate header, to make LLVMContextImpl.h
not hideous.  Also, fix some MSVC compile errors.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@78115 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/AsmParser/LLLexer.h b/lib/AsmParser/LLLexer.h
index de39272..667ab2c 100644
--- a/lib/AsmParser/LLLexer.h
+++ b/lib/AsmParser/LLLexer.h
@@ -24,7 +24,7 @@
   class MemoryBuffer;
   class Type;
   class SMDiagnostic;
-  class LLVMContext;
+  struct LLVMContext;
 
   class LLLexer {
     const char *CurPtr;