MINOR: init: emit warning when -sf/-sd cannot parse argument

Previously, -sf and -sd command line parsing used atol which cannot
detect errors.  I had a problem where I was doing -sf "$pid1 $pid2 $pid"
and it was sending the gracefully terminate signal only to the first pid.
The change uses strtol and checks endptr and errno to see if the parsing
worked.  It will exit when the pid list is not parsed.

[wt: this should be backported to 1.8]

src/haproxy.c

@@ -1445,13 +1445,27 @@ static void init(int argc, char **argv)
 				else
 					oldpids_sig = SIGTERM; /* terminate immediately */
 				while (argc > 1 && argv[1][0] != '-') {
+					char * endptr = NULL;
 					oldpids = realloc(oldpids, (nb_oldpids + 1) * sizeof(int));
 					if (!oldpids) {
 						ha_alert("Cannot allocate old pid : out of memory.\n");
 						exit(1);
 					}
 					argc--; argv++;
-					oldpids[nb_oldpids] = atol(*argv);
+					errno = 0;
+					oldpids[nb_oldpids] = strtol(*argv, &endptr, 10);
+					if (errno) {
+						ha_alert("-%2s option: failed to parse {%s}: %s\n",
+							 flag,
+							 *argv, strerror(errno));
+						exit(1);
+					} else if (endptr && strlen(endptr)) {
+						while (isspace(*endptr)) endptr++;
+						if (*endptr != 0)
+							ha_alert("-%2s option: some bytes unconsumed in PID list {%s}\n",
+								 flag, endptr);
+							exit(1);
+					}
 					if (oldpids[nb_oldpids] <= 0)
 						usage(progname);
 					nb_oldpids++;