glx: Check for byte-swapping in SetReplyHeader

Check for the need to byte-swap when attempting to display
GL apps between a big-endian server and little-endian client
or vice versa.

Fixes: https://gitlab.freedesktop.org/xorg/xserver/-/issues/1127

glx/vndcmds.c

@@ -92,6 +92,9 @@ static void SetReplyHeader(ClientPtr client, void *replyPtr)
     xGenericReply *rep = (xGenericReply *) replyPtr;
     rep->type = X_Reply;
     rep->sequenceNumber = client->sequence;
+    if (client->swapped) {
+	swaps(&rep->sequenceNumber);
+    }
     rep->length = 0;
 }