formatting.c cleanup - Mailing list pgsql-hackers

The file formatting.c contains some hard to read and understand code. 
For the attached patch series, I made a few more or less mechanical 
passes over it to modernize the code a bit, renamed some symbols to be 
clearer, adjusted some types to make things more self-documenting, 
removed some redundant code to make some things more compact.  I hope 
this helps a bit.