CToFormulaConverterWithPointerAliasing overwrote methode
makeFreshVariable but implemented it differently
(indices got added to variables that were never being treated as SSA
indices by other methods because of a different separator).
The one caller in the pointeraliasing package
also works with the original implementation of this method,
so we remove the overwrite and have only one implementation.

git-svn-id: https://svn.sosy-lab.org/software/cpachecker/trunk@13625 4712c6d2-40bb-43ae-aa4b-fec3f1bdfe4c