Blender Git Loki

BGE Fix: apply velocity clamping on every physics subtick

This patch uses the Bullet "internal tick callback" functionality to
ensure that velocity clamping is performed after every physics update.
This makes a difference when physics subticks > 1, as in that case the
too-high velocity could have impacted the simulation.

This patch follows the examples at [1] and [2]; the latter example
also explains that the way we limit velocity in the BGE (before this
patch) is wrong.

[1] http://bulletphysics.org/mediawiki-1.5.8/index.php/Simulation_Tick_Callbacks
[2] http://www.bulletphysics.org/mediawiki-1.5.8/index.php/Code_Snippets#I_want_to_cap_the_speed_of_my_spaceship;

Reviewed by: panzergame

Differential Revision: https://developer.blender.org/D1364