libsmacker: Add `smk_palette_updated` changes

This is a DevilutionX-specific patch to enable efficient rendering

3rdParty/libsmacker/smacker.c

@@ -1795,3 +1795,8 @@ char smk_seek_keyframe(smk s, unsigned long f)
 
 	return 0;
 }
+
+unsigned char smk_palette_updated(smk s)
+{
+	return s->frame_type[s->cur_frame] & 0x01;
+}

3rdParty/libsmacker/smacker.h

@@ -96,6 +96,9 @@ char smk_next(smk object);
 /** seek to first keyframe before/at N in an smk */
 char smk_seek_keyframe(smk object, unsigned long frame);
 
+/** was the pallet updated this frame */
+unsigned char smk_palette_updated(smk s);
+
 #ifdef __cplusplus
 }
 #endif