Two changes to Sema::LookupDecl() interface. 
(1) Remove IdLoc (it's never used). 
(2) Add a bool to enable/disable lazy builtin creaation (defaults to true).

This enables us to use LookupDecl() in Sema::isTypeName(), which is also part of this commit.

To make this work, I changed isTypeName() to be a non-const member function. I'm not happy with this, however I fiddled with making LookupDecl() and friends const and it got ugly pretty quickly. We can certainly add it back if/when someone has time to fiddle with it. For now, I thought this simplification was more important than retaining the const-ness. 

llvm-svn: 49087
diff --git a/clang/lib/Parse/MinimalAction.cpp b/clang/lib/Parse/MinimalAction.cpp
index 250fa76..9b2f351 100644
--- a/clang/lib/Parse/MinimalAction.cpp
+++ b/clang/lib/Parse/MinimalAction.cpp
@@ -52,7 +52,7 @@
 /// determine whether the name is a type name (objc class name or typedef) or
 /// not in this scope.
 Action::DeclTy *
-MinimalAction::isTypeName(const IdentifierInfo &II, Scope *S) const {
+MinimalAction::isTypeName(const IdentifierInfo &II, Scope *S) {
   if (TypeNameInfo *TI = II.getFETokenInfo<TypeNameInfo>())
     if (TI->isTypeName)
       return TI;