Create an own data class for the result of the PrecisionAdjustment.prec
method instead of using Triple.
This is shorter and easier to read code,
and provides more semantics than a plain triple.

git-svn-id: https://svn.sosy-lab.org/software/cpachecker/trunk@13128 4712c6d2-40bb-43ae-aa4b-fec3f1bdfe4c