[MAJOR] http: add support for option http-server-close

This option enables HTTP keep-alive on the client side and close mode
on the server side. This offers the best latency on the slow client
side, and still saves as many resources as possible on the server side
by actively closing connections. Pipelining is supported on both requests
and responses, though there is currently no reason to get pipelined
responses.
diff --git a/include/types/proxy.h b/include/types/proxy.h
index 92517ca..54190ee 100644
--- a/include/types/proxy.h
+++ b/include/types/proxy.h
@@ -100,12 +100,11 @@
 #define PR_O_TPXY_CLI	0x06000000	/* bind to the client's IP+port when connect()ing */
 #define PR_O_TPXY_MASK	0x06000000	/* bind to a non-local address when connect()ing */
 
-/* unused : tcpsplice   0x08000000 */
+#define PR_O_SERVER_CLO 0x08000000	/* option http-server-close */
 #define PR_O_CONTSTATS	0x10000000	/* continous counters */
 #define PR_O_HTTP_PROXY 0x20000000	/* Enable session to use HTTP proxy operations */
 #define PR_O_DISABLE404 0x40000000      /* Disable a server on a 404 response to a health-check */
 #define PR_O_ORGTO      0x80000000      /* insert x-original-to with destination address */
-/* unused: 0x80000000 - now used by PR_O_ORGTO */
 
 /* bits for proxy->options2 */
 #define PR_O2_SPLIC_REQ	0x00000001      /* transfer requests using linux kernel's splice() */