setup configure takes a --with-compiler option, but used to change 
that into a --with-hc option when calling ./configure.
Now that we've added autoconfUserHooks and deprecated defaultUserHooks we
can fix this without breaking any existing scripts. The autoconfUserHooks
now passes --with-compiler to ./configure and defaultUserHooks is unchanged.
Fixes ticket #114.

Setup scripts should switch to simpleUserHooks or autoconfUserHooks.
autoconfUserHooks now fails if ./configure is not present.
defaultUserHooks does the same thing it always did.

since you can get the same effect just by setting the command's default flags
to empty.

Also extend the check. It's now a QA error to use a license that is empty
or AllRightsReserved. It's a warning to not specify a license file. It's an
error for the license file to be given but not exist.
Note that QA errors are not fatal for generating tarballs. But they will become
fatal errors for uploading to the public hackage server. It will still be
possible to use AllRightsReserved or another license on a private hackagedb.

Code written in a session with Duncan Coutts

Much code written in a session with Duncan Coutts

Addresses #191 (QA) and #180 (QA for missing license).
This patch only adds a new exposed module, it's not yet used anywhere.

So they should be safe to remove now.

Fixed:
http://hackage.haskell.org/trac/hackage/ticket/176

because we use the value of configUserInstall to set the default value for
configPackageDB, and any value the user sets will override that.

Previously --user and --global didn't mean what it looks like they mean,
instead of doing a per-user or a global installation they just meant to
register in the per-user or global package databases (and to allow
dependencies to be satisfied from the per-user or global db)
With this patch --user / --global means to do a per-user or global install
so in addition to the package db differences it also sets the default 
installation prefix. This prefix can of course still be overridden using the
--prefix= flag. The global prefix is as before, the default per-user prefix
is $HOME/.cabal on Unix and on Windows it's something like:
C:/Documents And Settings/$user/Application Data/cabal
(using getAppUserDataDirectory "cabal"). This is the per-user prefix that
cabal-install currently uses. We can change it if people think it's not good.

but make it do something sensible with the ProgramConfiguration

Spotted by Spencer Janssen

for compatability with ghc-6.2.2

--list-options no takes priority over errors in other flags and over --help
this is so that it can be used consistently for command completion without
returning garbage (ie error messages on ill formed partial command lines
or producing --help output). Also make --list-options list all the common
options appart from itself, so that's just --help at the moment.

For the --enable/disable-optimi(z|s)ation flag, allow the British English
spelling of the flags as an alias. The current one is still the one
displayed, and it does not list bith in the --help text, though the command
completion would list both.
Perhaps the default should be on the basis of the current locale :-).

It applies at the top level in which case it lists the global flags and
the sub-commands. It applies for each sub-command in which case it lists
the sub-command's available flags.

And specify command flags in a way that allows converting from or two strings.
So not only can we parse command lines into the various flag types, we can
convert back. This is crucial in cabal-install so that we can call Setup.hs
scripts with all the various args, and override certain flags in a typed way
rather than just representing them all as strings.

Also move commandHelp out of the structure into a helper function. Change
the type of commandOptions so it doesn't include the CommonFlag. Instead,
add those in whenever necessary. This makes deriving commands easier.
Also fix docs.