git.el: Take into account the core.excludesfile config option.
git.el: Take into account the core.excludesfile config option.

Also don't require .git/info/exclude to exist in order to list unknown
files.

Signed-off-by: Alexandre Julliard <a3c1c71ac0d85b781251f68481a696b8e4d0781d@winehq.org>
Acked-by: Karl Hasselström <7985ada83f2f009c597f77bfcbafe8daa9e79c7d@treskal.com>
Signed-off-by: Junio C Hamano <a6723cc3f76163bf7adb636a73ac3b0ceb3e6b9b@pobox.com>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git