[AST] Traverse templates in LexicallyOrderedRecursiveASTVisitor

Summary:
We need to specialize this because RecursiveASTVisitor visits template
template parameters after the templated declaration, unlike the order in
which they appear in the source code.

Reviewers: arphaman

Reviewed By: arphaman

Subscribers: klimek, cfe-commits

Differential Revision: https://reviews.llvm.org/D36998

llvm-svn: 312631