multi-platform case_tolerant, finish windows

case_tolerant works locally, though this is fairly hard to write a good test for.  It's not like I can format a drive or anything.

Windows is done, mainly by porting P5 code.  I don't actually run Windows, so I'm not 100% sure it's all working -- functions that check the filesystem like rel2abs, abs2rel, and path need tested.

A couple of questions.  Since these modules are supposed to inherit from Unix.pm, shouldn't they all be "class File::Spec:* is File::Spec::Unix;"?  Does 64 bit Windows set $*OS as 'Win64'?  If so, that should be added to Win32.