This is in preparation of moving code out of weld.hxx
to separate headers/source files, in order to make it
easier to keep an overview and to avoid having to
recompile ~all UI code when anything changes.
Also move weldutils.cxx to a new vcl/source/weld
directory.
Change-Id: Ia75b42f21e560dd248307282a522f186a64cd742
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/195777
Tested-by: Jenkins
Reviewed-by: Michael Weghorn <m.weghorn@posteo.de>