Create CVoidType and use it instead of a CSimpleType with type void.
Having "void" sit besides INT etc.
and letting it have modifiers like long does not make sense.

git-svn-id: https://svn.sosy-lab.org/software/cpachecker/trunk@14369 4712c6d2-40bb-43ae-aa4b-fec3f1bdfe4c