avcodec/sanm: ignore codec45

Codec45 is used in some RA2 videos on top of codec37.

It consists of 2 tables (768 and 32768 bytes), and datapackets
like codec2 (delta-x, delta-y) with a pixel counter instead of a color value.
It then reads the 4 surrounding pixels, looks up 3 separate values
for each in table1, adds them together to form an index into
table2 for a new pixel value, in a row.

The data coming in gets the x/y coordinates out of the visible
area very quickly (2-3 iterations); I don't see any visual
difference between the ffmpeg-produced frames and ones captured
with dosbox from rebel assault 2, which leads me to believe this
codec never worked as intended.

Signed-off-by: Manuel Lauss <manuel.lauss@gmail.com>

libavcodec/sanm.c

@@ -1673,6 +1673,8 @@ static int process_frame_obj(SANMVideoContext *ctx, GetByteContext *gb)
         return old_codec23(ctx, gb, top, left, w, h, param, parm2);
     case 37:
         return old_codec37(ctx, w, h);
+    case 45:
+        return 0;
     case 47:
         return old_codec47(ctx, w, h);
     case 48: