Lemmih, Paolo Martini are the primary authors of cabal-install but were
missing from the list in LICENCE.

But it does not work yet as it need to be updated to take configurations into
account. At the moment it thinks no packages have any dependencies since
it does not finalise the configuration for the package.

Fixes a bug in my previous filepath patch

Follow directory layout of HackageDB data also when calculating URLs to download from, not just the local paths.

So it "Just Works"tm without needing extra options or sudo fiddling.
If you care you can still do sudo fiddling and --global-install

We can now install purely using cabal, no Makefile needed.
The install instrcutions previously said to install the data
file manually, but cabal does that for us now.

Fix the license, it's BSD3 not BSD4 (I double checked with Issac)
Have cabal install the serv.list for us as a data file.
Add HTTP and filepath as dependencies, rather than bundling them.

Enabled at -v2

So that at ordinary -v1 we do not get lots of silly warnings for outdated
.cabal files, like warnings about hs-src-dir vs hs-src-dirs.

This is relevant since we pass on this default verbosity when we call cabal,
so it's much better if they match up.

This should make it all "Just Work"tm. We no longer need a Makefile
to do the installation. The point is, don't bother trying to use
/etc/cabal-install/srve.list as the global list. That's hard to do
because it involves installing that file, and we only want to do that
for global installs, so it's even more complex. Instead we should just
use cabal's facility to install data files. That way it ends up in
/usr/local/share/cabal-install-x.y/
or somewhere similar for a user install. But either way, cabal handles it.
The per-user config sill overrides this one, so it's still possible to edit
the list even if /usr/local/share/ is read-only. Also, we always use
$HOME/.cabal-install/ for the per-user config and package cache.
The one downside is that if an admin wants to use /etc/ and /var rather
than /root/.cabal-install/ then this is a tad harder. But the point is
at the moment it'll at least work for most people without fiddling,
including windows users.

This is useful when you want to build a development version of something whose dependencies are available in Hackage. 

Before, getOpt would return a list of Flag, which had a one-to-one correspondence with functions TempFlags -> TempFlags. This made it uneccessarily difficult and error-prone to add new flags. I removed the Flag type and replaced the values with TempFlags -> TempFlags functions. This should have the side effect of making the tar path flag work, since it was not interpreted before.

See http://hackage.haskell.org/trac/ghc/ticket/3268
In new versions of ghc-pkg, ghc-pkg dump will emit an extra field like
pkgroot: /the/path/that/is/the/pkgroot
and other fields may contain ${pkgroot}, e.g.
library-dirs: ${pkgroot}/blah/
This allows relocatable packages, with package files installed
relative to the package database itself.

To allow parsers & pretty-printers for extensions of the format.

And add a TODO about future handling of OS variants like Android and iOS.

It has been deprecated in ghc-7.2
and ghc builds core libs with -Werror so we have to comply.