MINOR: connection: add flag MX_FL_FRAMED to mark muxes relying on framed xprt

In order to be able to check compatibility between muxes and transport
layers, we'll need a new flag to tag muxes that work on framed transport
layers like QUIC. Only QUIC has this flag now.
diff --git a/include/haproxy/connection-t.h b/include/haproxy/connection-t.h
index ca78196..77b43b8 100644
--- a/include/haproxy/connection-t.h
+++ b/include/haproxy/connection-t.h
@@ -280,6 +280,7 @@
 	MX_FL_HTX         = 0x00000001, /* set if it is an HTX multiplexer */
 	MX_FL_HOL_RISK    = 0x00000002, /* set if the protocol is subject the to head-of-line blocking on server */
 	MX_FL_NO_UPG      = 0x00000004, /* set if mux does not support any upgrade */
+	MX_FL_FRAMED      = 0x00000008, /* mux working on top of a framed transport layer (QUIC) */
 };
 
 /* PROTO token registration */
diff --git a/src/connection.c b/src/connection.c
index 2ead714..dd1898b 100644
--- a/src/connection.c
+++ b/src/connection.c
@@ -1707,6 +1707,9 @@
 		if (item->mux->flags & MX_FL_NO_UPG)
 			done |= fprintf(out, "%sNO_UPG", done ? "|" : "");
 
+		if (item->mux->flags & MX_FL_FRAMED)
+			done |= fprintf(out, "%sFRAMED", done ? "|" : "");
+
 		fprintf(out, "\n");
 	}
 }
diff --git a/src/mux_quic.c b/src/mux_quic.c
index 77bb7ae..4c240c8 100644
--- a/src/mux_quic.c
+++ b/src/mux_quic.c
@@ -1678,7 +1678,7 @@
 	.subscribe = qc_subscribe,
 	.unsubscribe = qc_unsubscribe,
 	.wake = qc_wake,
-	.flags = MX_FL_HTX|MX_FL_NO_UPG,
+	.flags = MX_FL_HTX|MX_FL_NO_UPG|MX_FL_FRAMED,
 	.name = "QUIC",
 };