>= saucy on kernel 3.4 and non-Atom Intel, downgrade mesa to version 8 (precise)

Discussed extensively in #704.

The tricky part is that `libegl1-mesa-drivers` was split in 2 parts, so there is a new `libwayland-egl1` package (required by kde). We create a fake package with `equivs` to work around that.

Tested in `2014-07-06_10-19-56_drinkcat_chroagh_x11test.tmp-pin-3.4-drivers_-R_precise-saucy-trusty_35`, output is here:
http://drinkcat.github.io/chroagh/2014-07-06_10-19-56_drinkcat_chroagh_x11test.tmp-pin-3.4-drivers_-R_precise-saucy-trusty_35.html
(3D acceleration is working on all platforms and Ubuntu releases)

@DennisLfromGA, @peter-gulka: Could you test this branch? In particular, I'm interested in KDE and Steam (testing Gnome, Unity, XFCE would be good too).
You can fetch the branch here: https://github.com/drinkcat/chroagh/archive/pin-3.4-drivers.zip, then extract and run `sudo sh installer/main.sh -n chrootname -u`
> Do we need all three of these, or do the updates or security repos effectively supersede the main repo for our needs?

Unfortunately we do... `libllvm3.0` is only in the core `precise` repo. All the others are in `precise-updates`, and we probably want `precise-security`, just in case.

> Adding another entire release to apt is pretty heavyweight and slows down the update process a lot...

We can always fetch the packages manually (`install_mirror_packages`), but the current approach has the advantage of pulling dependencies automatically (e.g. if somebody installs a x86 game, the right libraries will be pulled in, otherwise the user will get a version conflict that is not easy to resolve).

I already limited the impact quite a bit by fetching only the `main` component (i.e. removing `restricted universe multiverse`). I do agree it slows down the update process, I don't think it's "a lot" (I did not measure, and I guess the C710 with its spinning hard drive will probably suffer a bit).

The new sources need to be fetched the first time only, afterwards they will be up to date most the of time .

The increase in apt database size is about 38% (`precise` accounts for 18%, `precise-updates` 13% and `precise-security` 7%):
```
$ cat /var/lib/apt/lists/*precise*Packages | wc            
 779018 2347592 33516566
$ cat /var/lib/apt/lists/*trusty*Packages | wc 
2098825 6069268 88058344
```