Fix changing handling max gear to lower than current one crashing client

[forkerer]

Fixes #731
Changing vehicle max gear in handling to lower than current gear used by vehicle resulted in infinite loop in CTransmission:CalculateDriveAcceleration (0x6D05E0), i added a simple check to the beginning of the function, that lowers the gear if it's above maximum limit. The game doesn't freeze anymore.
This snippet helps with testing it:

function veh(client)
	setVehicleHandling(getPedOccupiedVehicle(client), "numberOfGears", 1)
end
addCommandHandler( "veh", veh )

[Einheit-101]

This never happened to me and i changed many max gears on my server, strange.

[qaisjp]