1. Exportable options ('export used') used to be exported if referred to in
a 'uses' statement. These options will now only be exported if the
option is set, or the default value is changed.
2. Options marked as 'export always' with no default value ('default none')
used to generate defines with no values 'export k8:='. This behavior
has changed so that the option will ONLY be exported if it has a value
assigned using 'set' or 'default'. Otherwise it is an error.
git-svn-id: svn://svn.coreboot.org/coreboot/trunk@1467 2b7e53f0-3cfb-0310-b3e9-8179ed1497e1
4f8311ae58