Packages can now be added/removed from an installed GHC as follows:

    $ ./ghc-inplace --list-packages
    gmp, rts, std, lang, concurrent, data, net, posix, text, util,
    hssource, win32, com, std2
    $ ./ghc-inplace --add-package <newpkg
    Reading package info from stdin... done.
    Saving old package config file... done.
    Writing new package config file... done.
    $ ./ghc-inplace --list-packages
    gmp, rts, std, lang, concurrent, data, net, posix, text, util,
    hssource, win32, com, std2, mypkg
    $ ./ghc-inplace --delete-package mypkg
    Saving old package config file... done.
    Writing new package config file... done.
    $ ./ghc-inplace --list-packages
    gmp, rts, std, lang, concurrent, data, net, posix, text, util,
    hssource, win32, com, std2

This is a first stab at the kind of functionality we need for
installing Haskell libraries via RPMs: the RPM script would install
the libraries, and then do a "ghc --add-package" passing the
appropriate paths.  You'd then have "ghc -package" at your disposal to
use the newly installed package.  Similarly on de-install, the RPM
script would run "ghc --delete-package".

Also in this commit: prettify the package dumping.