Introduced typedef for integral type associated with counting clauses.
Using "Var" for clause-length.
Introduced typedef for statistics-counting.
Correction: "Lit" instead of "int".
Improved types for unit-clause-stack.
Introduced typedef "Clause_index" (instead of "int").
Small improvements regarding type of changes-vector.
Introduced "Weight_t" (for the type of weights and their sum).
Version update.