Make the function pointer a template argument instead of a runtime value.

Summary:
Speed up the variadic matchers by removing one indirect call.
Making the function pointer a template arguments allows the compiler to
inline the call instead of doing an runtime call by pointer.
Also, optimize the allOf() case to avoid redundant kind checks.
This speeds up our clang-tidy benchmark by ~2%

Reviewers: klimek

Subscribers: klimek, cfe-commits

Differential Revision: http://reviews.llvm.org/D6424