chatzilla: Use firefox instead of xulrunner

Thanks to @nbp for pointing out that we don't need xulrunner anymore.

(cherry picked from commit 4de72baf03d1ad64eb9a724d2a36642c3fa17c3c)
chatzilla: Update to 0.9.91

(cherry picked from commit 71c34a45e18daa0d09b471fa616613ce6ec2c397)
Add openjdk to the small channel

(cherry picked from commit 4ecb762ee532889dd086ef9e95dea6e7488a57d8)
Remove obsolete Hydra package

(cherry picked from commit d4d0e449d7b96704eeaa2570255fb41c85c49613)
sqlite: Enable optimization

Commit a28940d9d542f3d7f2a5f88c4f2701a1818cf153 changed the SQLite
build to use CFLAGS instead of NIX_CFLAGS_COMPILE, but that's really
bad because it clobbers the default -O2 flag. So all this time we had
an unoptimized SQLite build. (This is one of the reasons why
NIX_CFLAGS_COMPILE exists - messing with CFLAGS is almost never a good
idea.)

(cherry picked from commit 2b5ccf8a53489f907116df3158c2354b99497bd1)
linux: Update to 3.12.31

(cherry picked from commit bac50c5c1fef4294035f2d78ddd0d412c9891dec)
Merge release 14.04 into backports.

* 'release-14.04' of github.com:NixOS/nixpkgs:
  linux: Update to 3.12.31
  sqlite: Enable optimization
  Remove obsolete Hydra package
  Add openjdk to the small channel
  chatzilla: Update to 0.9.91
  chatzilla: Use firefox instead of xulrunner