Add a patch to prevent gcc3 from removing /dev/null!

gcc 3.4.6 was removing /dev/null while building musl in stage 0.
I tracked down the bug, along with a patch to fix it.
Thanks to Gentoo and Mike Frysinger for the patch.
Merge pull request #108 from CMB/devnull

Ensure that gcc 3.4.6 doesn't remove /dev/null.