Damage bonks

[juef17]

This makes every bonk deal damage to the player. While a one-bonk-kill would be a real challenge, it is set at a more reasonable 1 damage at the moment. This is not quite done: if you're interested in such a feature, there's a few things to consider / change / add:

• To show that the player takes damage when bonking, there is an added red flash. If the no_flashing flags is on (which would disable the red flashes if using my previous pull request), the swamp damage sound is used instead of the bonking sound.
• I had intended to hook at the very same place that currently hooks to increment the bonk counter. I'm not sure what would be the best way to deal with these two features at the same time, so for this pull request to be more easily testable, I have commented out the bonk counter incrementation hook.
• To adhere to the game's intents, we should probably not do damage if the dragonlord is dead. I feel like this would not be a tough thing to implement but I figured it would make sense to first see if the damage bonks interest anyone at all.
• I have not properly commented the patched bytes for the bonk damage routine, but it's basically a copy/paste of the swamp damage routine with a rts byte at the end.

[Edit] Flag is implemented in this web app: here.