[Unison-hackers] Mac GUI

[Ben Willmore]

Hi folks,

SVN revision 133 (2.19.22) concludes my Mac GUI hackathon for the time
being.  I look forward to a blissful lack of bug reports.

I have:
* added a toolbar to perform common functions
* added a GUI for diffing files with help from Jerome
* added coloured indicators for the state of the reconItems
* fixed numerous GUI glitches

I have tried not to be inventive; I've just copied across all the
things that I missed from the GTK2 GUI.  So hopefully none of this
will cause any problems.

The only issue I am aware of is: I have always found the GTK2 GUI
confusing because it does not distinguish between conflicting
reconitems that the user has done nothing about, and conflicting
reconitems that the user has chosen to skip.  So, reconitems that I
have intentionally skipped are still marked with a red '?', making me
worry about them.  Therefore, in the Mac GUI, I have added a flag that
indicates when the user has actively decided to skip a conflicting
reconitem; such items are marked 'skip' rather than 'conflicts'.  This
makes a lot more sense to me; however, it is different from the GTK2
UI.  If this change is wrong somehow, or just if the difference
between the UIs is objectionable, I can of course get rid of the flag.

Now would be a great time for anyone who's interested to build, test
and complain about anything I messed up.

Ben