Stop the manual tracking of variables/UFs declared in SMTInterpol
while the solver stack was non-empty.
This does not work, because re-declaring them after the stack is pop'ed
actually creates a new independent declaration.
For supporting this we need to have support in SMTInterpol
for "global" declarations that do not get deleted when the stack is
pop'ed.

git-svn-id: https://svn.sosy-lab.org/software/cpachecker/trunk@14719 4712c6d2-40bb-43ae-aa4b-fec3f1bdfe4c