Removed Motif files that only contained stubs

  Removed Motif files that only contained stubs
for functionality that is:
1 - not Motif, but rather OS/WM specific:
    wxJoystick, wxWave, wxTaskBarIcon
2 - not provided natively by Motif:
    wxColourDialog, wxFontDialog, wxDirDialog,
    wxMetafile
3 - obsolete: wxTab*
4 - cruft: helpxxxx.h/cpp

  Regenerated configure and some filelist.txt-dependent
files.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@19907 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775