fix typo, thanks Qwell!

git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@7953 65c4cc65-6c06-0410-ace0-fbb531ad65f3

doc/CODING-GUIDELINES

@@ -384,7 +384,7 @@ in having code like this:
 However, the ast_strdup and ast_strdup functions will happily accept a NULL
 argument without generating an error.  The same code can be written as:
 	
-	newstr = strdup(str);
+	newstr = ast_strdup(str);
 
 
 * CLI Commands