Rip out TemplateIdRefExpr and make UnresolvedLookupExpr and

DependentScopeDeclRefExpr support storing templateids.  Unite the common   
code paths between ActOnDeclarationNameExpr and ActOnTemplateIdExpr.

This gets us to a point where we don't need to store function templates in
the AST using TemplateNames, which is critical to ripping out OverloadedFunction.

Also resolves a few FIXMEs.

llvm-svn: 89785