.gitignore: Ignore cscope.out

Similar file to 'tags', written by the cscope tool.

Signed-off-by: Andrew Price <anprice@redhat.com>
Reviewed-by: Jan Friesse <jfriesse@redhat.com>

.gitignore

@@ -26,6 +26,7 @@ ltmain.sh
 m4
 missing
 tags
+cscope.out
 ID
 Doxyfile
 test-driver