Add fprintf macro

I have applied the following patch:

Add fprintf() custom version to libpgport.

Document use of macros for pg_printf functions.

Bump major versions of all interfaces to handle movement of get_progname
from libpq to libpgport in 8.0, and probably other libpgport changes in
8.1.

-- 
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman@candle.pha.pa.us               |  (610) 359-1001
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