Ignore quilt .pc directory, used in deb packaging

Debian packaging uses quilt to manage patches. Book-keeping for them is
done using quilt (either directly, or in a compatible format), and
tracked in the directory .pc .

Change-Id: I22c90f3d7ab8918e6216e7b686de6fa0e1fdaa7b
Signed-off-by: Tzafrir Cohen <tzafrir.cohen@xorcom.com>