Merge pull request #295 from erwincoumans/master

fix a problem in the btMultiBodyConstraint related to self-collision, se...
replace unstable Gyroscopic force calculations with stable back Euler derived
update.  Removed max force clamping.
Fix a couple of bugs in 2dConvex Hull algorithm.
* Need to use atan2 so 3d angles are calculated properly after projection.
* Need to handle case where the first tripple of points is non-convex,
previously this would cause the algorithm to fail with only 1 point.
Revert "replace unstable Gyroscopic force calculations with stable back Euler derived"

This reverts commit 0ce687853def7e564ed71eca66cfe91a1ac604f7.
Merge pull request #297 from Orbots/convex-hull-fix

Convex hull fix
Merge remote-tracking branch 'bp/master'