Print drivers

[Philip Underwood]

I've got a rough demonstration of printing working for aven
This allows you to preview and print your files directly from aven,
using the wxWindows printing framework - seems to work quite well.

Download from http://www.furbrain.org.uk/survex-1.0.29-patch.tar.gz

untar it in your survex directory - It'll replace several files, and
create some new ones (printwx.cc printwx.h printui.c)
rerun automake, and it should all go swimmingly. Hopefully, I should be
able to get this all into CVS and a release.

Oh and I've added wheelmouse support for aven - wheel changes tilt of
view, although it's easy enough to change any other parameter...

Things needing to be done...

Give an option to "print it how it looks on the main screen"
-this seems to be the thing everyone wants. Coming soon...

Enable I18N support - I don't understand how it works in survex, so I've
just put everything in as static strings. This is obviously wrong, and I
hope I can get some directions as what to do. Most of the strings I want
have already got translations, I think...

General tidying up of the user interface - I think I need to redesign
the print dialog a bit - wxWindows seems very keen to bring up a further
print dialog box with page range and print to file options. I think I'll
just use this, so we'd have a two stage print dialog:

  svxPrintDialog - choose scale, view angle, which bits (legs etc)
  wxPrintDialog - choose which pages, print to file etc...