Fix collision multithreading inconsistency

Multithreading makes collisions be detected in different orders, causing
the clustering step of collision resolution to generate possibly
slightly different results on each run. This commit makes collision
order consistent.

Fix mistake in collision indexing

Fix incorrect poll function signature in rna_cloth.c

Merge branch 'master' into cloth-improvements

Merge branch 'master' into cloth-improvements

Merge branch 'master' into cloth-improvements

Copy cache when copying cloth object

Replace collision spinlocks with atomic_ops

Self collision refactor (prep for threading)

Multithread self collision detection

Multithread object collision detection

Collision refactor (prep for threading)

Implement cloth trouble indication map

This allows one to set a vertex group, to which "trouble" data is
written. This allows one to see where issues occured for instance in the
event of a cloth explosion.

Fix silly mistake in collision impulse clamping

Forgot to ignore clamping when set to zero, so collisions were just
being completely ignored at that value :

Fix vertex group influence UI

Fix blenderplayer linking

Implement collision impulse clamping (to prevent explosions)

Fix max subframe handling in adaptive subframes

Implement instability compensation

Fix critical collision bug

Collision object coordinates were not being updated when moving back in
time, causing simulation recalculations to somethimes have the collision
object only at the final position on the first simulated frame.

This also changes collision objects to use static bvh (like the cloth
bvh), which should cause a slight performance improvement.