Trivial fixes on error paths

* strace.c (startup_attach): Emit message on fork() failure.
(startup_child): Remove non-informative comment.
* util.c (ptrace_restart): use perror_msg() on error instead of fprintf().

Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>
diff --git a/strace.c b/strace.c
index fcdae0b..722a0f0 100644
--- a/strace.c
+++ b/strace.c
@@ -424,7 +424,7 @@
 	if (daemonized_tracer) {
 		pid_t pid = fork();
 		if (pid < 0) {
-			_exit(1);
+			perror_msg_and_die("fork");
 		}
 		if (pid) { /* parent */
 			/*
@@ -641,7 +641,7 @@
 # ifndef FREEBSD
 		pause();
 # else
-		kill(pid, SIGSTOP); /* stop HERE */
+		kill(pid, SIGSTOP);
 # endif
 #else /* !USE_PROCFS */
 		if (!daemonized_tracer) {