Allow disabling strafe jump accel bug in botlib/bspc

Need to enable proper code in PM_Accelerate and set libvar phys_strafejumping to 0 in game VM.
All bot AAS files need to be compiled using a cfg file with phys_strafejumping 0.

(Need for Turtle Arena.)
Merge remote-tracking branch 'spearmint/master'

Conflicts:
	code/botlib/be_aas_move.c
Use libvar phys_strafejumping 0