Remove the old way of completely disabling the use of floats.
The CtoFormulaConverter now always uses floats,
if the solver does not support them or we do not want them
they are transparently replaced with rationals.

git-svn-id: https://svn.sosy-lab.org/software/cpachecker/trunk@14531 4712c6d2-40bb-43ae-aa4b-fec3f1bdfe4c