fix(configure.ac): you must check for lib64

this fixes the build for fedora 18
fix(configure.ac): support ubuntu multilib

you must check the gcc -print-multiarch path also.
fix(configure.ac): support ubuntu multilib; support fedora using lib64
fix(configure.ac): placed a guard for ubuntu multilib inclusion on presence only
fix(configure.ac): fixed shell array [] for cofigure.ac to [[]], and typo
Merge pull request #26 from rackerlabs/coreos-fixup-multilib

fixup multilib and lib64 (updated)