Added a Lemke MLCP solver, extracted from the MBSim project, and re-licensed under the zlib license
with permission of the original author. 
The Lemke implementation is not fully working yet:
1) we need to convert the lo-high LCP problem into a problem without the lo/high
2) we need to sort out the remaining instabilities, and report a failure if the max loopcount is reached etc.
We replaced the fmatvec library with our own LinearMath/btMatrixX.h, and STL std::vector with btAlignedObjectArray

Removed some warnings/potential issues: use fuzzyZero instead of isZero, and some warnings, 
related to this issue 756


git-svn-id: http://bullet.googlecode.com/svn/trunk@2706 08e121b0-ae19-0410-a57b-3be3395fd4fd