Time Zone abbreviations in Brazil

[Paul Eggert]

Thanks for your info about Brazilian time zone abbreviations.
I'm inclined to change the tz database abbreviations from:

                std     dst
        -2:00   FST     FDT     Fernando de Noronha time
        -3:00   EST     EDT     Eastern Brazil time
        -4:00   WST     WDT     Western Brazil time
        -5:00   AST     ADT     Acre time

to:

                std     dst
        -2:00   FNT     FNST    Fernando de Noronha time
        -3:00   BRT     BRST    Brasilia time
        -4:00   WBT     WBST    Western Brazil time
        -5:00   ACT     ACST    Acre time

where `std' denotes standard time and `dst' denotes summer time.

The -3:00 row in the new table seems to match existing practice for
Brasilia time and Brasilia summer time.  I invented the
English-language abbreviations, and I also invented the other rows to
be consistent with the -3:00 row.  I believe that FN and AC are the
usual 2-letter abbreviations for Fernando de Noronha and Acre, so the
`WB' row is perhaps the most questionable abbreviation.

If this seems OK, I'll prepare a full patch along these lines;
comments and further suggestions are welcome.