Fix for selecting columns and floating table header
Fix for selecting columns and floating table header

Turn off floating table header on popup showing, turn it on (if it was
off) again when it is closed.
This has a negative side-effect of header disappearing behind the
content pane popup, but that is barely noticeable.

ultimate-pa/benchexec,bjowac/impara-benchexec,dbeyer/benchexec,sosy-lab/benchexec,ultimate-pa/benchexec,michkot/benchexec,bjowac/impara-benchexec,martin-neuhaeusser/benchexec,cheshire/benchexec,sosy-lab/benchexec,sosy-lab/benchexec,ultimate-pa/benchexec,dbeyer/benchexec,ultimate-pa/benchexec,sosy-lab/benchexec,IljaZakharov/benchexec,IljaZakharov/benchexec,martin-neuhaeusser/benchexec,bjowac/impara-benchexec,ultimate-pa/benchexec,martin-neuhaeusser/benchexec,ultimate-pa/benchexec,sosy-lab/benchexec,dbeyer/benchexec,IljaZakharov/benchexec,cheshire/benchexec,martin-neuhaeusser/benchexec,IljaZakharov/benchexec,cheshire/benchexec,michkot/benchexec,michkot/benchexec,dbeyer/benchexec,sosy-lab/benchexec