Build fix and add comments

src/boards/57.c

@@ -42,11 +42,9 @@ static void Sync(void) {
 	setchr8((regs[0] & 7) | (regs[1] & 7) | ((regs[0] & 0x40) >> 3));
 }
 
-#if 0
 static DECLFR(M57Read) {
 	return hrd_flag;
 }
-#endif
 
 static DECLFW(M57Write) {
 	switch (A & 0x8800) {

src/boards/69.c

@@ -89,6 +89,9 @@ static DECLFW(M69Write1) {
 	case 0xA: preg[1] = V; Sync(); break;
 	case 0xB: preg[2] = V; Sync(); break;
 	case 0xC: mirr = V & 3; Sync();break;
+	/* 17/10/17- reg $0D should awknowledge IRQ and no other
+	 * http://forums.nesdev.com/viewtopic.php?f=2&t=12436&start=15
+	 */
 	case 0xD: IRQa = V; X6502_IRQEnd(FCEU_IQEXT); break;
 	case 0xE: IRQCount &= 0xFF00; IRQCount |= V; break;
 	case 0xF: IRQCount &= 0x00FF; IRQCount |= V << 8; break;