Improve glob-win and support wildcards on Windows

I often use `mpv *.flac` in Linux, but this doesn't work in Windows. Most other Windows programs expand wildcards on the command line and it seems pretty easy to implement this in mpv by calling glob() on input files.

This rewrites the Windows glob implementation to be robust enough to be used this way and calls glob() on all command-line input files. Wildcard characters aren't allowed in normal Windows paths, so this shouldn't break on any paths that used to work.

Since it was a complete rewrite, and I referenced MSDN and POSIX instead of the old glob code, I updated the licence header in glob-win.c and glob.h. Is this the proper thing to do?