2.12.3 testing

[Graham Percival]

I tried making stable with the lilypond-release-branch.
Unfortunately, the ::lilypond-test target doesn't obey the
LILYPOND_BRANCH, so it built the 2.13.5 regtests.  As you would
expect, there was nothing in the comparison.  :(
Jan: I'll switch back to master, so it's not worth investigating
the problems on that branch.

I won't make any official release of a stable branch without
checking the regtest comparison.  And I don't even know if this
can compile the docs (I stopped the build).  And finally, I
commented out a number of critical errors in order to build the
installers, so who knows if the tarballs will even untar without
errors.


Still, if you're feeling adventurous, you could give these a spin.
Whatever crashes you get or failures score-compiling failures you
report can't hurt our efforts to have a release.

http://lilypond.org/~graham/
(don't grab the 2.13.5 by mistake; those definitely bomb)

Cheers,
- Graham