PR3558: mark "logically const" accessor methods in ASTContext as const,
and mark the fields they use as mutable. This allows us to remove a few
const_casts.

llvm-svn: 123314
diff --git a/clang/lib/AST/TemplateBase.cpp b/clang/lib/AST/TemplateBase.cpp
index 6d6fee6..42a936c 100644
--- a/clang/lib/AST/TemplateBase.cpp
+++ b/clang/lib/AST/TemplateBase.cpp
@@ -136,7 +136,7 @@
 }
 
 void TemplateArgument::Profile(llvm::FoldingSetNodeID &ID,
-                               ASTContext &Context) const {
+                               const ASTContext &Context) const {
   ID.AddInteger(Kind);
   switch (Kind) {
   case Null: