Added an option to turn off the optimization of assuming only values of zero or one for variables known to be boolean in a program: While this probably works fine for us internally, we need to turn it off for witness checking because other tools might assume other values than one for truth.

git-svn-id: https://svn.sosy-lab.org/software/cpachecker/branches/svcomp15@14203 4712c6d2-40bb-43ae-aa4b-fec3f1bdfe4c