apply: normalize path in --directory argument

apply: normalize path in --directory argument

When passing a relative path like --directory=./some/sub, the leading
"./" caused apply to prepend it literally to patch filenames, resulting
in an error (invalid path).
There may be more cases like this where users pass some/./path to the
directory which can easily be normalized to an acceptable path, so
these changes try to normalize the path before using it.

Signed-off-by: Joaquim Rocha <joaquim@amutable.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>