config: tcp_async alias for tcp_buf_write

- tcp_buf_write was not the best choosen name, so tcp_async was added as an
  alias for it

NEWS

@@ -273,9 +273,10 @@ new config variables:
      will be cached inside the process calling tcp_send (performance increase
      for sending over tcp at the cost of slightly slower connection closing and
      extra FDs kept open)
-  tcp_buf_write = yes | no (default no) - if enabled all the tcp  writes that 
+  tcp_async = yes | no (default no) - if enabled all the tcp  writes that 
      would block / wait for connect to finish, will be queued and attempted
      latter (see also tcp_conn_wq_max and tcp_wq_max).
+  tcp_buf_write = synonim for tcp_async
   tcp_conn_wq_max = bytes (default 32 K) - maximum bytes queued for write 
      allowed per connection. Attempting to queue more bytes would result
      in an error and in the connection being closed (too slow). If 

cfg.lex

@@ -301,7 +301,7 @@ TCP_MAX_CONNECTIONS	"tcp_max_connections"
 TCP_SOURCE_IPV4		"tcp_source_ipv4"
 TCP_SOURCE_IPV6		"tcp_source_ipv6"
 TCP_OPT_FD_CACHE	"tcp_fd_cache"
-TCP_OPT_BUF_WRITE	"tcp_buf_write"
+TCP_OPT_BUF_WRITE	"tcp_buf_write"|"tcp_async"
 TCP_OPT_CONN_WQ_MAX	"tcp_conn_wq_max"
 TCP_OPT_WQ_MAX		"tcp_wq_max"
 TCP_OPT_DEFER_ACCEPT "tcp_defer_accept"