Move the class out of weld.hxx into its own header, in
order to make it easier to keep an overview and to avoid
having to recompile ~all UI code when the class is
modified.
Change-Id: I2c8a9591a88ad26478243eb3f61214dc0efc51a1
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/196341
Reviewed-by: Michael Weghorn <m.weghorn@posteo.de>
Tested-by: Jenkins