[aprssig] FREQ SPEC minor update

[Bob Bruninga]

I just did a re-read of the APRS FREQ spec to make sure there were no
existing errors or confusion as a baseline.  I made a few wording changes to
better clarify some areas.  Here is the summary of changes at the top of the
file:  http://aprs.org/freqspec.txt

07 May 12 Clarifies some wording.  IE, MHz should be case sensitive for
transmit, and insensitive for receive.  Also added comments on observed
inconsistencies in the use of a leading space.  Better enumerated the 4
format categories for FREQ info:

1) FREQ OBJECTS - Freq in the object name for visibility on maps

2) Fixed Position COMMENT

3) STATUS Text - primarily for use in NMEA trackers

4) Auto-Inserted Freq Position Comment - for APRS radios

And removed the example of "FFF.FFF +" from the 2nd-10-byte field as too
many people were misinterpreting it and trying to make it parsable and
trying to apply it in the first 10 byte field. Where only FFF.FFxMHz is
allowed and it does not fit anyway..

Bob, Wb4APR