Cleanup. Remove Doug Lea's Malloc which is no longer used. We used to use dl malloc...

Cleanup. Remove Doug Lea's Malloc which is no longer used. We used to use dl malloc to give minisat a region of memory to allocate its data structures in. This meant that they were all close together in memory so that when cache line were stored, the lines would more often contain minisat data, rather than STP's data. However, Minisat 2.2 has a better allocator, so it allocates more of its stuff together in memory. The difference between the embedded minisat 2.2 in STP, and running it from the command line, is about 4%. Not a large enough difference to worry about.

git-svn-id: https://stp-fast-prover.svn.sourceforge.net/svnroot/stp-fast-prover/trunk/stp@1096 e59a4935-1847-0410-ae03-e826735625c1