Added defs for CentOS 5.9 and 6.4 boxes. Bugfix CentOS 5.8 x86_64 box.

CentOS 5.8 x86_64 box does not have RedHat_64 as type; this will cause a build failure as VirtualBox won't start properly.

Import box templates for CentOS 5.9 and CentOS 6.4.