Add CEGUI

Hi there,

As could easily be seen from #158, I’m currently working with [CEGUI](http://www.cegui.org.uk) on a project. I wanted to give back a bit for your nice help and wrote a MXE makefile for CEGUI so that others can benefit from the research I’ve done while working with it (and of course it makes it easier for other people in my project :-)).

My Makefile-fu isn’t that great, so I’m open to any comments on this.

Thanks for consideration :-)

Valete.

P.S: If you’re interested, the project I’m working on is [Secret Maryo Chronicles](http://secretmaryo.org) (code [here](https://github.com/Quintus/SMC)), a really nice jump’n’run game.