Add makeConst() template for other integral types

Summary: MacOSX doesn't know how to cast unsigned long to uint64_t :(

Be patient with it and add a template to hanbdle arbitrary integral types.

Reviewed By: @paulbiss

Differential Revision: D1686511

Signature: t1:1686511:1416344857:878d82abf31d83eec2692edddc9d379fa05d4e04