MEDIUM: checks: Implement redis check using tcp-check rules

A share tcp-check ruleset is now created to support redis checks. This way no
extra memory is used if several backends use a redis check.

The following sequence is used :

  tcp-check send "*1\r\n$4\r\nPING\r\n"

  tcp-check expect string "+PONG\r\n" error-status "L7STS" \
      on-error "%[check.payload(),cut_crlf]" on-success "Redis server is ok"
diff --git a/include/proto/checks.h b/include/proto/checks.h
index d0c827b..1c76a89 100644
--- a/include/proto/checks.h
+++ b/include/proto/checks.h
@@ -69,6 +69,8 @@
 int spoe_prepare_healthcheck_request(char **req, int *len);
 int spoe_handle_healthcheck_response(char *frame, size_t size, char *err, int errlen);
 
+int proxy_parse_redis_check_opt(char **args, int cur_arg, struct proxy *curpx, struct proxy *defpx,
+				const char *file, int line);
 #endif /* _PROTO_CHECKS_H */
 
 /*