engine: client: sanitize legacy protocol supported engine features flags

Do not enable what can't be enabled in current protocol.

engine/client/cl_parse.c

@@ -904,7 +904,7 @@ void CL_ParseServerData( sizebuf_t *msg, qboolean legacy )
 	background = MSG_ReadOneBit( msg );
 	Q_strncpy( gamefolder, MSG_ReadString( msg ), sizeof( gamefolder ));
 	host.features = (uint)MSG_ReadLong( msg );
-	host.features &= ENGINE_FEATURES_MASK;
+	host.features &= legacy ? ENGINE_LEGACY_FEATURES_MASK : ENGINE_FEATURES_MASK;
 
 	if( !legacy )
 	{

engine/common/protocol.h

@@ -305,6 +305,14 @@ extern const char	*clc_strings[clc_lastmsg+1];
 #define MAX_LEGACY_EDICTS (1 << MAX_LEGACY_ENTITY_BITS) // 4096 edicts
 #define MIN_LEGACY_EDICTS 30
 
+// legacy engine features that can be implemented through currently supported features
+#define ENGINE_LEGACY_FEATURES_MASK   \
+	( ENGINE_WRITE_LARGE_COORD    \
+	| ENGINE_LOAD_DELUXEDATA      \
+	| ENGINE_LARGE_LIGHTMAPS      \
+	| ENGINE_COMPENSATE_QUAKE_BUG \
+	| ENGINE_COMPUTE_STUDIO_LERP  )
+
 // Master Server protocol
 #define MS_SCAN_REQUEST "1\xFF" "0.0.0.0:0\0" // TODO: implement IP filter