musl-git: fine-tune check for existing checkout

the build process generates the directory, so the check suceeded always.
fix deps in some X11 libs
kernel-headers: bump to 3.12.6-3
libnettle: bump to latest
gnutls: bump to latest

requires latest libnettle.
this update fixes some serious security flaws:
http://lists.gnutls.org/pipermail/gnutls-devel/2014-March/006795.html
Update LuaJIT to 2.0.2
Merge pull request #193 from justincormack/luajit202

Update LuaJIT to 2.0.2
Add pixman as a qemu dependency

Although qemu ships with its own copy of pixman it will not build it with the version of autotools in sabotage so it is simpler to just add as a dependency and it will use the external copy.
Merge pull request #194 from justincormack/patch-1

Add pixman as a qemu dependency
python-pip needs wget

The download URL now redirects to https, which the busybox wget cannot cope with, so need the real wget.
Merge pull request #195 from justincormack/patch-2

python-pip needs wget
config.cache: update for latest musl
musl: bump to 1.0