Allow option aliasing. Lines of the form:
OLD_OPT = NEW_OPT
in options* files will now map OLD_OPT to NEW_OPT with a friendly
message. This is indented for situations where we need to preserve an
interface in the config file in an upwards compatible fashion on a
stable branch.
Reviewed by: nwhitehorn@
MFC after: 3 days
7a1b7e33b4