Whitespace.
Add ExplicitNamespaces and AllowAmbiguousTypes extensions
Merge remote-tracking branch 'upstream/master'
Replace 1.18.0.0 with 1.18.0 in 'bootstrap.sh'.

Fixes #1473.
sandbox init: warn instead of dying if there's a cabal-dev sandbox.

Fixes #1472.
Merge remote-tracking branch 'upstream/master'
Added the failing-node to the tree and the zipper.

Still need to do something meaningful in Validate.hs