[MEDIUM] http: add options to ignore invalid header names

Sometimes it is required to let invalid requests pass because
applications sometimes take time to be fixed and other servers
do not care. Thus we provide two new options :

     option accept-invalid-http-request  (for the frontend)
     option accept-invalid-http-response (for the backend)

When those options are set, invalid requests or responses do
not cause a 403/502 error to be generated.
diff --git a/include/types/proxy.h b/include/types/proxy.h
index 432b27b..b10fc10 100644
--- a/include/types/proxy.h
+++ b/include/types/proxy.h
@@ -112,6 +112,8 @@
 #define PR_O2_SPLIC_RTR	0x00000002      /* transfer responses using linux kernel's splice() */
 #define PR_O2_SPLIC_AUT	0x00000004      /* automatically use linux kernel's splice() */
 #define PR_O2_SPLIC_ANY	(PR_O2_SPLIC_REQ|PR_O2_SPLIC_RTR|PR_O2_SPLIC_AUT)
+#define PR_O2_REQBUG_OK	0x00000008      /* let buggy requests pass through */
+#define PR_O2_RSPBUG_OK	0x00000010      /* let buggy responses pass through */
 
 /* This structure is used to apply fast weighted round robin on a server group */
 struct fwrr_group {