Description:
------------
I propose to add the following simple modification to curl_multi_select() function. Now it is greatly miss the functionality to detect the timeout automatically.

ext\curl\multi.c:
...

PHP_FUNCTION(curl_multi_select)
{
	zval           *z_mh;
	php_curlm      *mh;
	fd_set          readfds;
	fd_set          writefds;
	fd_set          exceptfds;
	int             maxfd;
	double          timeout = 1.0;
	struct timeval  to;

	if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "r|d", &z_mh, &timeout) == FAILURE) {
		return;
	}

	ZEND_FETCH_RESOURCE(mh, php_curlm *, &z_mh, -1, le_curl_multi_handle_name, le_curl_multi_handle);

	_make_timeval_struct(&to, timeout);
+
+	/* If timeout == 0 is passed, detect it automatically. */
+	if (!to.tv_sec && !to.tv_usec) {
+		long max_tout = 1000;
+		if ((CURLM_OK == curl_multi_timeout(mh->multi, &max_tout)) && (max_tout != -1)) {
+			to->tv_sec = max_tout / 1000;
+			to->tv_usec = (max_tout % 1000) * 1000;
+		}		
+	}
+
	FD_ZERO(&readfds);
	FD_ZERO(&writefds);
	FD_ZERO(&exceptfds);

	curl_multi_fdset(mh->multi, &readfds, &writefds, &exceptfds, &maxfd);
	RETURN_LONG(select(maxfd + 1, &readfds, &writefds, &exceptfds, &to));
}


Reproduce code:
---------------
cURL has built-in ability to detect the minimal delay till a next handle timeout in the pool. But there is no chance to use this feature in PHP, because there is no such function. So we have to perform busy wait loops.

Expected result:
----------------
curl_multi_select($h, 0)
waits till the next request timeout at most.

Actual result:
--------------
there is no chance to catch a handle timeout without busy-wait loop now.