Reduce the number of symbols by changing how templates are instantiated per function bound in the registry.

Summary:
Reduce the number of symbols by changing how templates are instantiated per function bound in the registry.
This change reduces the number of sections in Registry.cpp.o by a little over 10%.

Reviewers: klimek

CC: cfe-commits, revane

Differential Revision: http://llvm-reviews.chandlerc.com/D1557