MEDIUM: checks: add send/expect tcp based check

This is a generic health check which can be used to match a
banner or send a request and analyse a server response.
It works in a send/expect ways and many exchange can be done between
HAProxy and a server to decide the server status, making HAProxy able to
speak the server's protocol.

It can send arbitrary regular or binary strings and match content as a
regular or binary string or a regex.

Signed-off-by: Baptiste Assmann <bedis9@gmail.com>
diff --git a/include/types/server.h b/include/types/server.h
index 6b73a39..82eb55f 100644
--- a/include/types/server.h
+++ b/include/types/server.h
@@ -122,6 +122,7 @@
 	char desc[HCHK_DESC_LEN];		/* health check descritpion */
 	int use_ssl;				/* use SSL for health checks */
 	int send_proxy;				/* send a PROXY protocol header with checks */
+	struct tcpcheck_rule *current_step;     /* current step when using tcpcheck */
 	int inter, fastinter, downinter;        /* checks: time in milliseconds */
 	int result;				/* health-check result : SRV_CHK_* */
 	int state;				/* health-check result : CHK_* */