Compiler capabilities clean-up
- renamed CATCH_SFINAE -> CATCH_CONFIG_SFINAE
- moved variadic macros detection into catch_compiler_capabilities.h
Build 36
- incorporation of pull request #154 to allow comparison with nullptr_t
- some compiler capability tweaks
Merge commit '4dd3f68dd930fdb9f26c1776118e663908864931' into merge-up-int

Conflicts:
	include/internal/catch_sfinae.hpp
Build 36

Merge commit '471eba2c32abe6811cdc2acddfbeb0032d0b5fe9' into merge-up-int

Conflicts:
	README.md
	include/internal/catch_evaluate.hpp
	single_include/catch.hpp