BTOR: Fix on BV not having same width after rewriting.
BTOR: Fix on BV not having same width after rewriting.

This covers only Equals. Most likely, there are other cases in which
this needs to be checked. For this reason, an ad-hoc function is
provided.

More testing is required.

agriggio/pysmt,pysmt/pysmt,pysmt/pysmt,agriggio/pysmt