Starting on the OSX client

We've created an Xcode project in the client directory, which will house
the OSX client program.  Not much there yet, just wanted to get the files
committed into this new branch.
Moving things to UI-specific directories

We're building the base of the client to be UI-independent, and have the
UI just reference the base stuff as necessary.  Most of the motif-specific
stuff is in motif/, and the OSX-specific 'r9' directory was renamed to
osx/.
Merge branch 'osx-client'