add Bool theory support.

  definitions in smtlib-bv driver.
- Add no-bv.gen driver file targeted to provers without support for
  the smtlib bv theory (or for the no_bv variants).
- update realization & tests

Isabelle2015 is still supported, but support for Isabelle2014 has been
discontinued.

split the ppat_ghost field in program patterns into two distinct
conditions:
- ppat_ghost, indicating that the pattern starts as ghost,
  meaning that all variables in it are ghost, too;
- ppat_fail, meaning that the pattern contains a refutable
  ghost subpattern, which makes the match in the extracted code
  impossible, which makes the whole match expression ghost.

Until now, the two conditions were disjunctively combined, making
admissible the invalid pattern matching in bench/p/b-d/ghost4.mlw.

If the answer of prover was unknown and reason of the answer was not None
and the proof was edited, it was not marked as obsolete. This commit
fixes this problem.

Contributed by Stefan Berghofer.