t4014 test used GNU extension 'Q' in its sed scripts, but the
uses can safely be replaced with 'q'. Among other platforms,
sed on Mac OS X 10.4 does not accept the former.
Signed-off-by: Steffen Prohaska <prohaska@zib.de> Signed-off-by: Junio C Hamano <gitster@pobox.com>