use square epsilon in btVector3::fuzzyZero (length2)

git-svn-id: http://bullet.googlecode.com/svn/trunk@2707 08e121b0-ae19-0410-a57b-3be3395fd4fd
make Lemke work with lower/upper bounds, using the BLCP to LCP conversion (using a dog-slow matrix inversion etc)
for this conversion, see also https://github.com/erwincoumans/num4lcp/blob/master/matlab/test_lcp_bounds.m and
appendix A1 in http://www.cs.duke.edu/~parr/nips10.pdf, thanks to Kenny Erleben and Evan Drumwright for the tips!
(friction is not coupled to normal forces yet)


git-svn-id: http://bullet.googlecode.com/svn/trunk@2708 08e121b0-ae19-0410-a57b-3be3395fd4fd