[R-SIG-Mac] rgl revisions to allow dual install

[Duncan Murdoch]

I've just committed some changes to rgl to allow it to install two 
versions of its shared library on Mac OSX, one
for AGL and one for X11.  The build process ended up kind of messy, and 
I'm not sure it will work on ppc or other different Mac platforms.

This hasn't been sent to CRAN yet, but I've put a temporary build on my 
own web page at

http://www.stats.uwo.ca/faculty/murdoch/temp/rgl_0.69.535.tar.gz

Could someone else try installing this, and confirm it works 
transparently both in the GUI and from the console?

Thanks to Simon for inspiring this and providing some advice (though I 
couldn't get his cleaner solution to work; not sure why not).

Duncan Murdoch