SH-4274 FIX Adding RegionHandshakeReply flags for SSA

Adding a flag to hint to the sim that this viewer knows how to handle
AvatarAppearance messages for self in SSA-enabled regions.

Upstream patch: 5fdc790f6d

indra/newview/llviewerregion.cpp

@@ -1621,7 +1621,11 @@ void LLViewerRegion::unpackRegionHandshake()
 	msg->addUUID("AgentID", gAgent.getID());
 	msg->addUUID("SessionID", gAgent.getSessionID());
 	msg->nextBlock("RegionInfo");
-	msg->addU32("Flags", 0x0 );
+
+	U32 flags = 0;
+	flags |= REGION_HANDSHAKE_SUPPORTS_SELF_APPEARANCE;
+
+	msg->addU32("Flags", flags );
 	msg->sendReliable(host);
 }