MINOR: h1: Add H1_MF_XFER_LEN flag

This flag is usefull to handle cases where there is no body, regardless of CL or
TE headers (for instance, responses to HEAD requests). It will not be set by the
parser itself.
diff --git a/include/types/h1.h b/include/types/h1.h
index ec967ac..2abf472 100644
--- a/include/types/h1.h
+++ b/include/types/h1.h
@@ -144,6 +144,7 @@
 #define H1_MF_CONN_CLO          0x00000020 // message contains "connection: close"
 #define H1_MF_CONN_KAL          0x00000040 // message contains "connection: keep-alive"
 #define H1_MF_CONN_UPG          0x00000080 // message contains "connection: upgrade"
+#define H1_MF_XFER_LEN          0x00000100 // message xfer size can be determined
 
 /* Note: for a connection to be persistent, we need this for the request :
  *   - one of CLEN or CHNK