Function sync_timeout_check

src/custom.cpp:5528–5536

#define LLV_DEBUG 0

static bool sync_timeout_check(frame_time_t max)
{
#if LLV_DEBUG
	return true;
#else
	frame_time_t rpt = read_processor_time();
	return rpt - max <= 0;
#endif
}

extern int busywait;
static void scanlinesleep(int currline, int nextline)