Merge branch 'ab/free-and-null'

A common pattern to free a piece of memory and assign NULL to the
pointer that used to point at it has been replaced with a new
FREE_AND_NULL() macro.

* ab/free-and-null:
  *.[ch] refactoring: make use of the FREE_AND_NULL() macro
  coccinelle: make use of the "expression" FREE_AND_NULL() rule
  coccinelle: add a rule to make "expression" code use FREE_AND_NULL()
  coccinelle: make use of the "type" FREE_AND_NULL() rule
  coccinelle: add a rule to make "type" code use FREE_AND_NULL()
  git-compat-util: add a FREE_AND_NULL() wrapper around free(ptr); ptr = NULL

split-index.c

@@ -167,10 +167,9 @@ void merge_base_index(struct index_state *istate)
 
 	ewah_free(si->delete_bitmap);
 	ewah_free(si->replace_bitmap);
-	free(si->saved_cache);
+	FREE_AND_NULL(si->saved_cache);
 	si->delete_bitmap  = NULL;
 	si->replace_bitmap = NULL;
-	si->saved_cache	   = NULL;
 	si->saved_cache_nr = 0;
 }