mingw: do not bother to test funny file names

mingw: do not bother to test funny file names

MSYS2 actually allows to create files or directories whose names contain
tabs, newlines or colors, even if plain Win32 API cannot access them.
As we are using an MSYS2 bash to run the tests, such files or
directories are created successfully, but Git itself has no chance to
work with them because it is a regular Windows program, hence limited by
the Win32 API.

With this change, on Windows otherwise failing tests in
t3300-funny-names.sh, t3600-rm.sh, t3703-add-magic-pathspec.sh,
t3902-quoted.sh, t4016-diff-quote.sh, t4135-apply-weird-filenames.sh,
t9200-git-cvsexportcommit.sh, and t9903-bash-prompt.sh are skipped.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>