Platform Truncation Fixes/Additions

/cc @opscode/release-engineers @lamont-granquist @barnabear
@lamont-granquist no opensuse is `MAJOR` only while sles is `MAJOR.MINOR`. See the [OHAI-339](https://tickets.opscode.com/browse/OHAI-339) for all the dirty details. I also did some digging on the project sites.

AIX is `MAJOR.MINOR`.