MINOR: htx: Add BODYLESS flags on the HTX start-line and the HTTP message

the flags HTX_SL_F_BODYLESS and HTTP_MSGF_BODYLESS have been added. These flags
are set when the corresponding HTTP message has no body at all.
diff --git a/include/types/htx.h b/include/types/htx.h
index 6d64c13..1146b9a 100644
--- a/include/types/htx.h
+++ b/include/types/htx.h
@@ -81,6 +81,7 @@
 #define HTX_SL_F_CLEN          0x00000008 /* The content-length header was found in message */
 #define HTX_SL_F_CHNK          0x00000010 /* The message payload is chunked */
 #define HTX_SL_F_VER_11        0x00000020 /* The message indicates version 1.1 or above */
+#define HTX_SL_F_BODYLESS      0x00000040 /* The message has no body (content-length = 0) */
 
 /* HTX flags */
 #define HTX_FL_NONE              0x00000000
diff --git a/include/types/proto_http.h b/include/types/proto_http.h
index 0f341e2..9e8bbd5 100644
--- a/include/types/proto_http.h
+++ b/include/types/proto_http.h
@@ -148,6 +148,8 @@
 #define HTTP_MSGF_WAIT_CONN   0x00000010  /* Wait for connect() to be confirmed before processing body */
 #define HTTP_MSGF_COMPRESSING 0x00000020  /* data compression is in progress */
 
+#define HTTP_MSGF_BODYLESS    0x00000040  /* The message has no body (content-length = 0) */
+
 
 /* Redirect flags */
 enum {