1. Options can only be set with 'option' statement in the target
configuration file. Options can be set as many times as needed.
2 Option DEFAULT values can be changed (or set) in any configuration file.
Changing a default value will display a warning message.
3. A default value is changed with the statement 'default <op> = <val>'.
4. Setting an option overrides the default value.
5. The 'mainboard' and 'arch' statements now set options implicitly. No
'uses' statement is required.
The idea is that parts will define default values for options that
they need/use. Option overrides are only done in the target file.
git-svn-id: svn://svn.coreboot.org/coreboot/trunk@1258 2b7e53f0-3cfb-0310-b3e9-8179ed1497e1
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