use nullptr in MSVC from 2005+
(based on PR #307 - thanks alex85k)
Merge branch 'develop' of github.com:philsquared/Catch into develop

# By Andy Sawyer
# Via Andy Sawyer (1) and Phil Nash (1)
* 'develop' of github.com:philsquared/Catch:
  catch_tostring: tostring for enum class types
  SelfTest: Build as C++11, add EnumToString tests
  SelfTest: refresh makefile
Merge branch 'develop' of github.com:philsquared/Catch into develop

# By Andy Sawyer
# Via Andy Sawyer (1) and Phil Nash (1)
* 'develop' of github.com:philsquared/Catch:
  Updated CMakeLists.txt for toString work
  A bunch of Catch::toString tests
Changed time function name to reflect that it actually returns Microseconds as reported in #323
Added baselines for new test cases
build 3