* Clean-up permanent monster spawn:
- <delay1>,<delay2>,<event> are actually optionnal field
- <event> value 0 and 1 are meaningless (actually event name with length < 4 are skipped)
* Exported monster AI constants
* Updated docs for monster size constants (already exported)
Notes:
- the default size for monster script cmd was small not medium
- monster script cmd now display a warning for size above SZ_BIG (previously SZ_ALL)
* - Fixed an issue to make <xs> and <ys> optionnals
- Updated npcs scripts
* Leftover in the docs for permanent monster spawn
* Corrected english docs. Credit to @aleos89
Added additionnal warning for xs / ys negative input. Credit @Lemongrass3110
Thanks to @cydh for the idea
