Initial support both ASCII and UNICODE builds on Windows.

This requires using a different character type for Windows (TCHAR), as well as
a string literal wrapper (TEXT) and alternative string function names (_tcs*).

To not break POSIX and to avoid spoiling the global namespace, I've made
simple wrappers prefixed with _tinydir_ for all of these things.

This is rather ugly, admittedly.
Replace uses of _MSC_VER with _WIN32.

_MSC_VER checks the compiler, not the platform. Compilers other than Microsoft's can be used
to build Win32 applications.
Merge branch 'windows-unicode'
Merge branch 'win32-macro-fix'

Conflicts:
	tinydir.h