crda: add regulatory domain stream parser

This adds a stream parser for regulatory domains. This
allows developers to build regulatory domains now using
the db.txt from a stream, either stdin, or a from an
opened file.

This also adds a simple db2rd which for now only uses the
library but with a bit of effort can also be used as a
suitable replacement for the kernel's genregdb.awk.

Signed-off-by: Luis R. Rodriguez <mcgrof@do-not-panic.com>
4 files changed