Installed a custom error handler for Z3.

Upgraded Z3 version to 60aad7a6623182eddc63d949cee4fde98922c65d,
latest version before the interpolation interface was changed.

git-svn-id: https://svn.sosy-lab.org/software/cpachecker/trunk@14547 4712c6d2-40bb-43ae-aa4b-fec3f1bdfe4c