Implement effects of 'mutable', and a few comments from Chris on its parsing.

llvm-svn: 59470
diff --git a/clang/lib/AST/DeclCXX.cpp b/clang/lib/AST/DeclCXX.cpp
index 4037404..6be9eaf 100644
--- a/clang/lib/AST/DeclCXX.cpp
+++ b/clang/lib/AST/DeclCXX.cpp
@@ -22,9 +22,9 @@
  
 CXXFieldDecl *CXXFieldDecl::Create(ASTContext &C, CXXRecordDecl *RD,
                                    SourceLocation L, IdentifierInfo *Id,
-                                   QualType T, Expr *BW) {
+                                   QualType T, bool Mut, Expr *BW) {
   void *Mem = C.getAllocator().Allocate<CXXFieldDecl>();
-  return new (Mem) CXXFieldDecl(RD, L, Id, T, BW);
+  return new (Mem) CXXFieldDecl(RD, L, Id, T, Mut, BW);
 }
 
 CXXRecordDecl::CXXRecordDecl(TagKind TK, DeclContext *DC,