status: Quote paths with spaces in short format

status: Quote paths with spaces in short format

According to the documentation for git-status, in short-format mode,
paths with spaces or unprintable characters are quoted. However
28fba29 (Do not quote SP., 2005-10-17) removed the behavior that quotes
paths that have spaces but not unprintable characters. Unfortunately this
makes the output of `git status --porcelain` non-parseable in certain
(rather unusual) edge cases. In the interest of removing ambiguity when
parsing the output of `git status --porcelain`, restore the behavior of
quoting paths with spaces in git-status's short-format mode.

Signed-off-by: Kevin Ballard <kevin@sb.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>