Consistently use "superproject" instead of "supermodule"

We fairly consistently say "superproject" and never "supermodule" these
days. But there are seven occurrences of "supermodule" left in the current
work tree. Three appear in Release Notes for 1.5.3 and 1.7.7, three in
test names and one in a C-code comment.

Replace all occurrences of "supermodule" outside of the Release Notes
(which shouldn't be changed after the fact) with "superproject" for
consistency.
Signed-off-by: NJens Lehmann <Jens.Lehmann@web.de>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

t/t7408-submodule-reference.sh

@@ -28,7 +28,7 @@ git prune'
 
 cd "$base_dir"
 
-test_expect_success 'preparing supermodule' \
+test_expect_success 'preparing superproject' \
 'test_create_repo super && cd super &&
 echo file > file &&
 git add file &&
@@ -55,7 +55,7 @@ diff expected current'
 
 cd "$base_dir"
 
-test_expect_success 'cloning supermodule' \
+test_expect_success 'cloning superproject' \
 'git clone super super-clone'
 
 cd "$base_dir"

t/t9300-fast-import.sh

@@ -1657,7 +1657,7 @@ M 160000 :6 sub
 INPUT_END
 
 test_expect_success \
-	'P: supermodule & submodule mix' \
+	'P: superproject & submodule mix' \
 	'git fast-import <input &&
 	 git checkout subuse1 &&
 	 rm -rf sub && mkdir sub && (cd sub &&

unpack-trees.c

@@ -1209,7 +1209,7 @@ static int verify_uptodate_1(struct cache_entry *ce,
 			return 0;
 		/*
 		 * NEEDSWORK: the current default policy is to allow
-		 * submodule to be out of sync wrt the supermodule
+		 * submodule to be out of sync wrt the superproject
 		 * index.  This needs to be tightened later for
 		 * submodules that are marked to be automatically
 		 * checked out.