[xmonad] new decoration framework status

[Andrea Rossato]

Hi,

I've just sent a message about the nature of my latest (I hope not
useless) code.

This is a brief statu report:

I checked and ported almost all instances of LayoutClass except:

- XMonad.Layout.MultiToggle: I never used it, I don't have a clear
  idea of what is supposed to do so I'm reluctant to touch code I
  don't know.

- XMonad.Layout.PerWorkspace: I've never used and I must confess I
  don't understand layout combinators very well, so the same of the
  above..;) But I'm sure Brent can do that in a second.

- XMonad.Layout.ToggleLayouts: I didn't have time but I came to read
  David's code quite well (moreover I've already hacked David's
  combinators and ported LayoutCombinators), so that's very easy and
  I'll do that shortly (before pushing anyway).

The rest should be just fine. The only incompatibility with old
configurations is due to the fact that the type of the tabbed
configuration has changed, and tabSize has been removed.

"tabbed shrinkTest defaultTConf" is working fine, since TConf is not
exported and I wrote the code to convert it into the new
configuration. But it will fail in case of record update of
defaultTConf, since fields are not exported (they would clash with the
new decoration configuration system). The type signature of the function
is changed too, but we do not usually invite user to write them down,
so this should not be an issue.

I tested XMonad.Config.* and they seem to be working just fine.

I think this is it.

Andrea