Added optimal left/right strafing.  No line strafing and other types of
strafing yet.
Added optimal line strafing and fixed some bugs.

Implemented tas_yaw and tas_pitch, but no punchangle compensation yet.
override_ols is also implemented.  No backpedalling by +back for now.  In
addition, if the speed is zero then the optimal angle is always 0 regardless of
L, A and pm_wishspeed.  This is to avoid getting NaN thus causing the game to
hang.