Merge 6 stable

Merges most of 6-stable into master. Remaining files which need merge:

lib/ohai/plugins/cloud.rb
lib/ohai/plugins/gce.rb
spec/unit/plugins/gce_spec.rb

Also, the spec tests for aix plugins need to be done up version 7 style.

@sersut Can you take a look at/help me with the remaining files that need to be merged? For some reason I'm having trouble determining what to keep and what to change... I can fix the broken aix tests tomorrow/weekend/definitely before Monday.