Fix a bug in PredicateCPA when the value of parameters of the entry
function is relevant.
If there was no assignment to the parameters, they were not in the
SSAMap, and thus instantiate and uninstantate did not work for them,
so the predicates over these variables did never hold.
This is now fixed for the entry function.
A similar problem occurs when the analysis starts in the middle of the
CFA at an arbitrary function, and for this case the problem is not fixed
(we currently do not have analysis that use this case).
A workaround for such cases is to set
cpa.predicate.useParameterVariables=true,
which will probably become the default anyway at some point.

git-svn-id: https://svn.sosy-lab.org/software/cpachecker/trunk@13381 4712c6d2-40bb-43ae-aa4b-fec3f1bdfe4c