Add changes required to compile with MS VC6

Add macro UNITTEST_COMPILER_IS_MSVC6
Add macro UNIITEST_NS_QUAL_STD(fun)
Avoid __pragma()
Skip tests with long long
Merge remote-tracking branch 'remotes/upstream/master'
Adapt MemoryOutStream for VC6 __int64 type
Merge pull request #43 from martinmoene/master

Add changes required to compile with MS VC6