Remove the port files and references to it from the common headers and
elsewhere.
Also remove GPE (GNOME PDA Environment) support as libgpewidget is
unmaintained since 2006 or so and has never been really used.
Use __WXGTK__ to test for any version of wxGTK now. Still define
__WXGTK20__ for compatibility, but always define it now and don't test
for it in the library code.
This port hasn't been updated for ages and is not used by anybody any
longer, so remove its code to facilitate maintenance.
Also remove references to this port from the documentation and most of
the other places (VMS-specific descrip.vms files still check for it
because it's not clear how to update them all), including configure.
Regenerate the latter and rebake all makefiles.
Finally document that this port is not available any longer.
Fix the bug introduced in ec0734f96f (Install DLLs in bindir, not
libdir, when using MSW toolchains, 2021-01-09): the directory where the
DLLs were installed wasn't created any more, resulting in errors if it
didn't exist.
Update to latest bakefile version adding the missing mkdir command to
fix this and also use a released bakefile version for the wx makefiles.
Regenerate configure to match the new version.
See #14601.
This basically removes the "adv" library, even though it's still
preserved for compatibility with user make/project files referring to
it.
It is done because the distinction between "adv" and "core" was never
really clear (e.g. why wxTreeCtrl was in core but wxTreeListCtrl in
adv?) and it prevented some core classes from using adv ones.
