* Takes function(player, mo) input.
* Return TRUE for stating that yes, the player is in a state that can cause contact damage, do with that what you will.
* Return FALSE for stating that no, the player is weak and vulnerable and cannot cause contact damage, do with that what you will.
* Return NIL for allowing the function to continue regular operation.

Fills a different ideological niche than ShouldDamage - that's for determining whether damage dished between two objects should happen, this is for determining which way around damage should be dished when considering a player-object interaction.

Or, in other words, think of it as "ShouldDamage is whether damage that has been requested should be granted, for object-object interaction, while PlayerCanDamage is for whether global player properties should cause damage to enemies and monitors in the first place, like spinning, hammering or stomping."

Remove mute boolean from playermsg hook, fix username stuff still being there, potential memory leaks, and added back the ip message.

# Conflicts:
#	src/lua_hook.h
#	src/lua_hooklib.c
#	src/p_user.c

# Conflicts:
#	src/lua_hook.h

# Conflicts:
#	src/lua_hook.h
#	src/lua_hooklib.c

Smiles follow-mobj initial support! Still using a Lua hook to follow closely behind, but now it doesn't need to be a generic thinkframe. Woo!

Also slightly edited P_XYMovement to properly check the mobj still exists before checking its eflags for MFE_SPRUNG, while I was at it

Generic mobj hooks are now run before mobjtype-specific mobj hooks, and player/linedef executor hooks now have their own lists

Adding ShieldSpecial hook. (Activates under different circumstances to the JumpSpinSpecial hook, and can be used to cancel existing shield actions.)

Restructured things so nojumpdamage characters can use the elemental, bubblewrap and attract shields.

Add "damagetype" argument to functions for Lua hooks ShouldDamage, MobjDamage, MobjDeath and HurtMsg

* When moving slowly, P_InstaThrust at S_SKIN's maxdash forward, and set momz to S_SKIN's mindash upwards. Plays a tok noise (not thok). Hurts enemies/bosses, busts spikes/monitors/all types of bustable blocks.
* When moving quickly... doesn't do anything yet, but WILL do a slide.

Also, P_DoSpinDash is now renamed to P_DoSpinAbility, and CA_TWINSPIN users can bust all bustable blocks on collision too.

(no actual SLOC changes)

This _should_ solve some significant performance
issues Lua experiences. If not, I will be very
upset for having wasted so much time and effort.

There will be bugs, this kind of thing needs to
be thuroughly tested and this is just the first
iteration of it.