Spawning/saving fixes, improved debugging

Fixed some issues with new accounts spawning and using the tutorial.

IsNewPlayer now returns a correct value for the player's first session.

Added OnPlayerSpawnNewCharacter, called when a player actually spawns as
a new character, not just when they enter the creation screen
(OnPlayerCreateNewCharacter).

Fixed virtual world and interior setting when spawning new characters.

Added debugging code to Vehicle/Interact.pwn due to a report of a
possible vehicle interaction issue.

Changed debug calls to use va_formatex instead of va_format so the extra
specifiers such as %p work properly now.