Merge branch 'jc/codingstyle-compare-with-null'

Doc update.

* jc/codingstyle-compare-with-null:
  CodingGuidelines: do not ==/!= compare with 0 or '\0' or NULL

Documentation/CodingGuidelines

@@ -232,6 +232,18 @@ For C programs:
         while( condition )
 		func (bar+1);
 
+ - Do not explicitly compare an integral value with constant 0 or '\0',
+   or a pointer value with constant NULL.  For instance, to validate that
+   counted array <ptr, cnt> is initialized but has no elements, write:
+
+	if (!ptr || cnt)
+		BUG("empty array expected");
+
+   and not:
+
+	if (ptr == NULL || cnt != 0);
+		BUG("empty array expected");
+
  - We avoid using braces unnecessarily.  I.e.
 
 	if (bla) {