mercurial 2.9.2

Updated to Mercurial 2.9.2

Closes #28204.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>
setuptools 3.4.1

Closes #28195.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>
python: update 2.7.6 bottle.
juju 1.18.0.
juju: update 1.18.0 bottle.

Closes #28182.

Signed-off-by: Adam Vandenberg <flangy@gmail.com>
Initialize cxxstdlib set lazily

This is used rarely and only at build-time, so we don't need to create
it when instantiating the formula.
sqlite 3.8.4.3
sqlite: update 3.8.4.3 bottle.
aria2 1.18.5
aria2: update 1.18.5 bottle.
sqsh: use Formula[]
nzbget: use resources
cairo: switch to recommended dep

I'm tired of looking at this issue, and I doubt too many people are
using "without-x" anyway. Sorry!

Fixes #25175.
Rework make_relative_symlink error handling and move it into keg
Raise useful errors from make_relative_symlink
Only unlink after a LinkError
Raise AlreadyLinkedError when a keg is already linked
Adjust link command for updated error handling
Adjust installer for updated link error handling