ed(1): make WARNS=6 clean

Although argc and argv are never read after the longjmp is complete,
gcc is not clever enough to see that and needlessly warns about it.
So add volatile to silence the compiler.

Approved by:	ed (the co-mentor, not ed(1))

bin/ed/Makefile

@@ -4,7 +4,6 @@
 
 PROG=	ed
 SRCS=	buf.c cbc.c glbl.c io.c main.c re.c sub.c undo.c
-WARNS?=	2
 LINKS=	${BINDIR}/ed ${BINDIR}/red
 MLINKS=	ed.1 red.1
 

bin/ed/main.c

@@ -103,15 +103,10 @@ const char usage[] = "usage: %s [-] [-sx] [-p string] [file]\n";
 
 /* ed: line editor */
 int
-main(int argc, char *argv[])
+main(volatile int argc, char ** volatile argv)
 {
 	int c, n;
 	long status = 0;
-#if __GNUC__
-	/* Avoid longjmp clobbering */
-	(void) &argc;
-	(void) &argv;
-#endif
 
 	(void)setlocale(LC_ALL, "");