config,completion: add color.status.unmerged

Reported-by: "Mladen B." <mladen074@gmail.com>
Signed-off-by: Michael J Gruber <git@drmicha.warpmail.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

contrib/completion/git-completion.bash

@@ -2014,6 +2014,7 @@ _git_config ()
 		color.status.changed
 		color.status.header
 		color.status.nobranch
+		color.status.unmerged
 		color.status.untracked
 		color.status.updated
 		color.ui