The mingw-w64 runtime expands wildcards, which causes a discrepancy
between `main`'s `argv` (multiple file names) and Windows' `wargv` (a
single wildcard). Use `wmain` to retrieve the wide character args.
Windows regards the `NUL` device as tty, which causes `WriteFile` to
fail (the bytes written pointer cannot be `NULL` in this case). Tweak
the color test to ensure tty is accurate.
Windows 10 supports color output, but it must be explicitly enabled;
ANSICON provides support for other versions. Enable color if either of
those are available. Resolves#1494.
Jason Hood