[EAS] ALL USA FIPS CODE; converter boxes

[Sean Donelan]

Even very old boxes used by over-the-air broadcasters are unlikely to
crash-n-burn with "000000".  Exactly how they handle every header
code combination is less clear, because the FCC hasn't defined the 
correct behavoir in some corner cases.  But no one is expecting (except
by accident) those corner cases.

Simple cases like national EAN or NPT haven't had problems for OTA 
systems.  As always, you should check with your vendor's support or
bench test it yourself.

Cable/wireline TV systems are more complicated and use a wider variety
of systems.  They are more likely to have issues driving head-end 
management systems and downstream set-top boxes, etc. if those aren't 
expecting the "000000" geographic code.