[mod_fastcgi,mod_scgi] backend spawn EINTR retry (#2788)

When spawning backends, retry blocking connect() to backend if EINTR
received when attempting to see if backend is already running.  EINTR
might be received if a HUP or USR1 signal is received while connecting
(or SIGCHLD on systems without SA_RESTART)

(expected to occur extremely rarely, but simple to handle properly)

x-ref:
  "FreeBSD/1.4.45/SSL: requests getting stuck in handle-req state occasionally"
  https://redmine.lighttpd.net/issues/2788

src/mod_fastcgi.c

@@ -1001,7 +1001,10 @@ static int fcgi_spawn_connection(server *srv,
 		return -1;
 	}
 
-	if (-1 == connect(fcgi_fd, fcgi_addr, servlen)) {
+	do {
+		status = connect(fcgi_fd, fcgi_addr, servlen);
+	} while (-1 == status && errno == EINTR);
+	if (-1 == status) {
 		/* server is not up, spawn it  */
 		pid_t child;
 		int val;

src/mod_scgi.c

@@ -771,7 +771,10 @@ static int scgi_spawn_connection(server *srv,
 		return -1;
 	}
 
-	if (-1 == connect(scgi_fd, scgi_addr, servlen)) {
+	do {
+		status = connect(scgi_fd, scgi_addr, servlen);
+	} while (-1 == status && errno == EINTR);
+	if (-1 == status) {
 		/* server is not up, spawn in  */
 		pid_t child;
 		int val;