Merge branch 'ep/maint-equals-null-cocci'

Introduce and apply coccinelle rule to discourage an explicit
comparison between a pointer and NULL, and applies the clean-up to
the maintenance track.

* ep/maint-equals-null-cocci:
  tree-wide: apply equals-null.cocci
  tree-wide: apply equals-null.cocci
  contrib/coccinnelle: add equals-null.cocci

ewah/bitmap.c

@@ -218,7 +218,7 @@ int bitmap_is_subset(struct bitmap *self, struct bitmap *other)
 
 void bitmap_free(struct bitmap *bitmap)
 {
-	if (bitmap == NULL)
+	if (!bitmap)
 		return;
 
 	free(bitmap->words);