[AD] Code consistency across platforms

[Evert Glebbeek <eglebbk@xxxxxxxxxx>]

While comparing the code used on different platforms, I noticed that  
very similar tasks are sometime performed very differently on  
different platforms. In the case of OS X, this is sometimes necessary  
because of the use of Objective-C, but in other cases it appears to be  
just random or personal preference of whoever wrote the code.
This isn't a big problem, but from a maintainability point of view it  
might be a good idea to compare how different operations are  
implemented on different platforms and try to "unify" the approach  
somewhat. This will also make it easier to implement things or fix  
bugs across different platforms by people who are not as familiar with  
some of them.

Another consistency point:
on OS X we have:
qzmouse.m
keybd.m
osxgl.m
system.m

On X11 the equivalent files are
xmousenu.c
xkeyboard.c
xdisplay.c / xsystem.c (both contain equivalent functions to osxgl.m,  
maybe also xglx_config.c)
xsystem.c

On Windows:
wmouse.c
wkeybdnu.c
wgl_disp.c/wnewwin.c
wnewsys.c

(Windows of course also has the D3D driver in d3d_disp.cpp)

And we have the generic UNIX files
umouse.c
ukeybd.c
usystem.c

That should probably also be synchronised a bit. It would be nice if  
functions for certain tasks can be found together in certain files on  
each platform, but the way some platforms work may make this hard  
(don't know, but I suppose it could).
I don't think we actually need a platform prefix ("x", "w", "osx") for  
these files, since they're all in their own subdirectories, but it  
might be useful in some cases.

I would suggest the following "standard" filenames across platforms  
(with or without prefix):

mouse
keyboard
opengl (or plain gl)
system
cursor
joy (or joystick?)

Thoughts?

Also, there seem to a lot of old/unused files still around, for  
instance in the OS X port. Is it ok to remove these to get rid of some  
of the clutter?

Evert