Sometimes I want to remove only Coccinelle's results, but keep all
other build artifacts left after my usual 'make all man' build.  This
new 'cocciclean' make target will allow just that.
Signed-off-by: NSZEDER Gábor <szeder.dev@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>