Instead of going through a global callback function set the string table's default gender at the start of each frame

This will perform the CVAR lookup only once per frame, not once per string.

src/common/engine/i_interface.h

@@ -31,7 +31,6 @@ struct SystemCallbacks
 	FString(*GetPlayerName)(int i);
 	bool (*DispatchEvent)(event_t* ev);
 	bool (*CheckGame)(const char* nm);
-	int (*GetGender)();
 	void (*MenuClosed)();
 	bool (*CheckMenudefOption)(const char* opt);
 	void (*ConsoleToggled)(int state);