*: use "can't" instead of "cannot"

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

networking/udhcp/signalpipe.c

@@ -29,7 +29,7 @@ static void signal_handler(int sig)
 {
 	unsigned char ch = sig; /* use char, avoid dealing with partial writes */
 	if (write(signal_pipe.wr, &ch, 1) != 1)
-		bb_perror_msg("cannot send signal");
+		bb_perror_msg("can't send signal");
 }