[ax25-layer2] 7-byte address proposal

[Michael Huslig]

Just for fun:

An 8 character upper-case "Callsign",  where the first 3 characters are 
numbers or letters, the 4th character is a number, letter, or space, and the 
5th through 8th characters are letters or space, can be encoded uniquely 
into 40 bits.

36*36*36*37*27*27*27*27=0xD599FFE340

Mike