- Updates Linux notifications to use current libnotify.

- Fix build problems on Mac OS X using autotools
- Consistently use #if HAVE_X for platform checks,
    rather than #ifdef HAVE_X or #if defined(HAVE_X)
- In Unix build, make lots of compiler checks standard
- Fix some compile warnings

From Matt Arsenault.

Note: there are now lots of compile warnings in clientgui/ on Unix,
    mostly in WxWidgets code


svn path=/trunk/boinc/; revision=24303