Fix deprecated QString::SkipEmptyParts
This fixes the various warnings related to QString::SkipEmptyParts
that is deprecated since Qt
version 5.14.0
. I used a common header to define a preprocessor macro PV_QT_SKIP_EMPTY_PARTS
that gets evaluated based on the current Qt version pv is compiled with.
This MR also fixes a previous big that I introduced.
@keu-sciviz @yohann.bearzi @ben.boeckel