Added Dantzig MLCP solver option from Open Dynamics Engine (trying to avoid naming/linking conflicts in case ODE and Bullet is used together)
If an MLCP solver fails, use PGS/SI fallback, add a boolean return value for 'solve' method

git-svn-id: http://bullet.googlecode.com/svn/trunk@2688 08e121b0-ae19-0410-a57b-3be3395fd4fd
fix compile errors

git-svn-id: http://bullet.googlecode.com/svn/trunk@2689 08e121b0-ae19-0410-a57b-3be3395fd4fd