Updating CryptoMiniSat2 to r494. The only difference between this

Updating CryptoMiniSat2 to r494. The only difference between this
version and the version in SVN is that performReplace() is not called
here. The reasons for this are:

1) performReplace() is at the moment buggy when MiniSat is used as a
   library

2) For a programmable solver, we need to have all variables to
   propagating at all times, thus we cannot accept to have certain
   variables acting as more than one (for which performReplace is
   used)

git-svn-id: https://stp-fast-prover.svn.sourceforge.net/svnroot/stp-fast-prover/trunk/stp@443 e59a4935-1847-0410-ae03-e826735625c1