Build 68: fixes, small HUD enhancements

• added options menu item to hide key bind legend
• HUD quest icon now shows X/Y quests completed tally so you don't have to open the quests screen

• fixed VM abort (crash) during map compatibility checks on vanilla E1M9 and MAP16

• fixed VM abort when talking to a bossbrain in a level with no monsters, eg doom2 map30 on HMP difficulty

Also worth noting, GZDoom 4.0 has just been released and contains a fix for a ZScript problem that some of you reported, please upgrade!