libtriple: implement fast forward in cPlayback()

First try at implementing fast forward. Needs more love.
Reverse does not work yet, setting speed to negative values
right now simply resets to "play" mode.

libtriple/video_td.h

@@ -179,6 +179,7 @@ class cVideo
 		void SetVideoMode(analog_mode_t mode);
 		void SetDBDR(int) { return; };
 		void SetAudioHandle(void *) { return; };
+		void FastForwardMode(int mode = 0);
 		void SetAutoModes(int [VIDEO_STD_MAX]) { return; };
 		int  OpenVBI(int) { return 0; };
 		int  CloseVBI(void) { return 0; };