Update x11/xscreensaver to 5.29.

>From the changelog:

5.29    * Downgraded to Xcode 5.0.2 to make it possible to build savers
          that will still run on 10.6 and 10.7.  Sigh.
        * Updated `webcollage' for recent changes.

5.28    * Fixed some compilation problems and intermittent crashes.
        * Turned off the OSX 10.6 enable_gc hack. It didn't work.

5.27    * New hacks, `tessellimage' and `projectiveplane'.
        * Added support for pthreads, because Dave Odell is a madman.
        * Updated `webcollage' for recent changes.
        * Minor iOS tweaks to the `analogtv' hacks.
        * X11: Don't assume Suspend = 0 implies "No DPMS".
        * Minor updates to `boxed' and `klein'.
        * Fixed possible crash in `apple2', `noseguy', `xmatrix', `shadebobs'.
        * Fixed possible crash in OSX preferences.
        * OSX Performance improvements.
        * Plugged some leaks.

5.26    * More auto-updater tweaks.

5.25    * Try harder to bypass Quarrantine and Gatekeeper in OSX installer.
        * Some files were missing from the tarball.

5.24    * Added "Automatically check for updates" option on OSX.
        * Updated feed-loading for recent Flickr changes.
        * Updated `webcollage' for recent Google changes.
        * Added Instagram and Bing as `webcollage' image sources.
        * Updated to latest autoconf.
        * Bug fixes.

5.23    * New hack, `geodesic'.
        * iOS and OSX: huge XCopyArea performance improvements.
        * More heuristics for using RSS feeds as image sources.
        * Improved Wikipedia parser.
        * Updated `webcollage' for recent Flickr changes.
        * Added Android to `bsod'.
        * OSX: Added a real installer.
        * iOS and OSX: fixed a font-metrics bug.
        * iOS: Fixed aspect ratio bug in non-rotating apps when launched in
          landscape mode.
        * Made `quasicrystal' work on weak graphics cards.
        * iOS: fixed `ifs'.
        * Better compression on icons, plists and XML files: smaller
          distribution and installation footprint.
        * Reverted that DEACTIVATE change. Bad idea.
        * `Phosphor' now supports amber as well as green.

(hauke)