cpu: get blarg CPU instruction test 6 passing

Its been too long since a checkin, but here's some of the
improvements:

- Support for diffing with other emulators
- Better disassmbed output
- New CPU instructions implemented
- Lots of CPU fixes

src/gbemu/video.c

@@ -106,14 +106,19 @@ out:
 
 void gb_video_cycle(struct gb_video *video, int cycles)
 {
+	static int screenshot_count = 0;
+
 	video->line_counter += cycles;
 	if (video->line_counter >= CYCLES_PER_LINE) {
 		video->line_counter -= CYCLES_PER_LINE;
 		video->curline += 1;
 		if (video->curline > LCD_Y_MAX) {
 			video->curline = 0;
-			if (video->lcdcont & 1 << 7) {
-				gb_video_screenshot(video);
+			if (video->lcdcont & (1 << 7)) {
+				screenshot_count++;
+				if (screenshot_count % 30 == 0) {
+					gb_video_screenshot(video);
+				}
 			}
 		}
 	}
@@ -164,7 +169,7 @@ void gb_video_mem_write(struct gb_video *video, uint16_t addr, uint8_t val)
 	uint8_t *write_addr;
 
 	if (video->debug_logging) {
-		gb_log("Video[%x]=%x\n", addr, val);
+		gb_log("Write Video[%x]=%x\n", addr, val);
 	}
 
 	switch (addr) {