Refactor rounding of numbers in table-generator
Refactor rounding of numbers in table-generator

Decimal.adjusted() is a nice simplification,
and an additional variable makes the code easier to read.
We also add some assertions.

ultimate-pa/benchexec,sosy-lab/benchexec,ultimate-pa/benchexec,ultimate-pa/benchexec,ultimate-pa/benchexec,sosy-lab/benchexec,sosy-lab/benchexec,dbeyer/benchexec,sosy-lab/benchexec,dbeyer/benchexec,sosy-lab/benchexec,dbeyer/benchexec,sosy-lab/benchexec,ultimate-pa/benchexec,dbeyer/benchexec,ultimate-pa/benchexec