message: support to listen unix socket.
diff: @@ -30,9 +30,10 @@ ZEND_BEGIN_ARG_INFO_EX(arginfo_swoole_process_pool_on, 0, 0, 2)
  ZEND_ARG_INFO(0, callback)
  ZEND_END_ARG_INFO()
  -ZEND_BEGIN_ARG_INFO_EX(arginfo_swoole_process_pool_listen, 0, 0, 2)
  +ZEND_BEGIN_ARG_INFO_EX(arginfo_swoole_process_pool_listen, 0, 0, 1)
  ZEND_ARG_INFO(0, host)
  ZEND_ARG_INFO(0, port)
  + ZEND_ARG_INFO(0, backlog)
  ZEND_END_ARG_INFO()
  static PHP_METHOD(swoole_process_pool, __construct);
  @@ -328,7 +329,7 @@ static PHP_METHOD(swoole_process_pool, listen)
  RETURN_FALSE;
  }
  - if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "sl|ll", &host, &l_host, &port, &backlog) == FAILURE)
  + if (zend_parse_parameters(ZEND_NUM_ARGS() TSRMLS_CC, "s|ll", &host, &l_host, &port, &backlog) == FAILURE)
  {
  return;
  }
  @@ -340,14 +341,17 @@ static PHP_METHOD(swoole_process_pool, listen)
  }
  SwooleG.reuse_port = 0;
  - if (swProcessPool_create_tcp_socket(pool, host, port, backlog) < 0)
  + int ret;
  + //unix socket
  + if (strncasecmp("unix:/", host, 6) == 0)
  {
  - RETURN_FALSE;
  + ret = swProcessPool_create_unix_socket(pool, host + 5, backlog);
  }
  else
  {
  - RETURN_TRUE;
  + ret = swProcessPool_create_tcp_socket(pool, host, port, backlog);
  }
  + SW_CHECK_RETURN(ret);
  }
  static PHP_METHOD(swoole_process_pool, start)
  