Create symbolic expressions for equal operations like for all others in Value Analysis.

Previously, equal-operations were handled by just calling .equals(Object) on the symbolic values.
This resulted in "false" being assigned to variables if symbolic values differed - which is obviously false, in general.



git-svn-id: https://svn.sosy-lab.org/software/cpachecker/branches/symbolic@15008 4712c6d2-40bb-43ae-aa4b-fec3f1bdfe4c