Teach psql to display comments on languages and casts.

The output of \dL (list languages) is fairly narrow, so we just always
display the comment.  \dC (list casts) can get fairly wide, so we only
display comments if the new \dC+ option is specified.

Josh Kupershmidt

src/bin/psql/command.c

@@ -381,7 +381,7 @@ exec_command(const char *cmd,
 				success = listConversions(pattern, show_system);
 				break;
 			case 'C':
-				success = listCasts(pattern);
+				success = listCasts(pattern, show_verbose);
 				break;
 			case 'd':
 				if (strncmp(cmd, "ddp", 3) == 0)