CodingGuidelines: style for multi-line comments

The style for multi-line comments is often mentioned and should be documented
for clarity.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>

Documentation/CodingGuidelines

@@ -145,6 +145,14 @@ For C programs:
    they were describing changes.  Often splitting a function
    into two makes the intention of the code much clearer.
 
+ - Multi-line comments include their delimiters on separate lines from
+   the text.  E.g.
+
+	/*
+	 * A very long
+	 * multi-line comment.
+	 */
+
  - Double negation is often harder to understand than no negation
    at all.