Add PlayerSpawn hook to Lua
I don't know how I did this but I did. Something about staring at code from 3AM till 5AM...
Here's a test script too:
```Lua
addHook("PlayerSpawn", function(player) player.health = 99 end)
```
See merge request !48
BACKPORT: removal of music slots
Relevant commits cherry-picked. Basically everything except the internal music track name switches.
See merge request !43
(No, game, you can't allocate a map header for the credits, why were you doing that before and how did it not break anything??)
(cherry picked from commit e1f9a012297d5220dcdd9395265467621a170e32)
Use whatever names you want for your music. So long as you prefix the lumps with O_ or D_, it doesn't matter anymore.
DISCLAIMER: Linedef type 413 (change music) and Lua scripting is not tested.
(cherry picked from commit 025ca413a2a01a8ec7c104748c2f510e350aa457)
# Conflicts:
# src/p_user.c
g_game.c: In function 'G_CheckDemoStatus':
g_game.c:5588:22: warning: logical not is only applied to the left hand side of comparison [-Wlogical-not-parentheses]
if (!modeattacking == ATTACKING_RECORD)
^
