WIN1250 as server encoding

Some people have requested to add WIN1250 as an allowed server encoding.  
So far, the order of the encoding numbers determined which ones were 
client-only, so in order not to renumber the encodings, I could only 
come up with the attached ugly solution.  If no one thinks of a better 
one, we'll go with that.

It would also be good if someone who has an environment that calls for 
WIN1250 (that is, Windows and an appropriate language environment) 
could test whether this actually does anything besides compiling 
without errors. :)

-- 
Peter Eisentraut
http://developer.postgresql.org/~petere/