Restructure outfuncs and readfuncs to use macros in the same style as

just done for copyfuncs/equalfuncs.  Read functions in particular get
a lot shorter than before, and it's much easier to compare an out function
with the corresponding read function to make sure they agree.
initdb forced due to small changes in nodestring format (regularizing
a few cases that were formerly idiosyncratic).

Author: tglsfdc