Remove the removed workaround again for x86-64

Removed workaround to prevent vehicle script server crashes

Removed drive mode toggle because GMod can't deal with it anymore apparently.

- Seats and turrets can no longer be picked up/tooled
- Refactored some code a little
- Passengers now exit properly in the back instead of the gunner's position
- Passengers are properly thrown out of the APC during removal

Fix for the latest update

Added z_secondary_magnitude.

Added new features and concommands per request.

- zapc_togglehatch: Allows remote (un-)locking of the hatch, up to zapc_remote_lock_distance yards away (using 'remotelock' permission).
- zapc_enterhatch: Tries to move directly into the passenger bay, even if we were allowed as driver.
- If you press +walk while +use'ing an (empty) APC and the hatch is opened, you will enter the passenger bay. Otherwise, nothing happens.

A proper documentation on the client (with a list of cvars, commands and usage) is currently planned and will be released at some point in the future.

Happy I'mnotgoingtomakeahelicoptermas!

Moved to the new publishing tools and have a few changes:
+ Added several convars on the server to modify the APC's behaviour.
+ Added rocket ignition and shhhh sound.
* The APC is now found under 'Vehicles' and no longer under 'Entities'. Yes, that took some time.

! Fixed 2345610112 ("attempt to index local 'k' (a number value)". Stop abusing _G.

! Attempt to fix various bugs reported by the GMod error tool (exclusive the gibmod bug).