Porting all changes from forl to master branch

* fixes for DRUP (forgot to dump some data during implication cache
  cleaning)
* fixes for regression tester (we can now do checking of results on
  whole directories again)
* fixes for speed of DRUP: '\n' instead of << endl
* fixes for deleting &std::cout when in DRUP-debug mode
* addition of clause database sorter for DRUP debug