CODING: update style guide for multiline comments

Document the preferred style for multiple line comment blocks and give an
example.

Change-Id: I73d6183da9014a943316e5aea1d43be2acc81ad7
Reviewed-on: https://gerrit.openafs.org/12361
Reviewed-by: Benjamin Kaduk <kaduk@mit.edu>
Tested-by: Benjamin Kaduk <kaduk@mit.edu>

CODING

@@ -83,6 +83,16 @@ Suggested compiler flags:
 		(You might not want the -fd, it isn't really useful, just complains about the
 		K&R style functions, but -v gives useful info.)
 
+Multiple line comment blocks should begin with only /* on one line and end with
+only */ on one line.
+
+Example:
+
+	/*
+	 * Multiple line comment blocks should be formatted
+	 * like this example.
+	 */
+
 
 Dependencies required to build OpenAFS from source
 --------------------------------------------------