Reject filenames that would be invalid on Windows

[fingolfin]

For a time, hap was shipping with a file named :q, specifically lib/Functors/:q, which apparently causes trouble on Windows (CC @ChrisJefferson). Clearly that file was created by accident while using vim or a similar editor.

Ideally ReleaseTools (and the PackageDistro tools) would reject problematic filenames like these. I guess at the very lest : and \ should be prevented. Maybe more. Perhaps also special filenames like CON / AUX / ... (also in different case variants; see https://learn.microsoft.com/en-gb/windows/win32/fileio/naming-a-file?redirectedfrom=MSDN) should be rejected.