Log Message:
PR 52787: fix postgres kerberos handling. Tuck the kerberos support
(whether "kerberos" or "gssapi") within an option so it can \ 
be turned
off. For 92/93 this is the existing "kerberos" option; for 94+ this
is the "gssapi" option instead, to satisfy the one person who cares
about the distinction.

For postgresql92 and 93 the kerberos option is now on by default (it
wasn't before, only the "gssapi" code has been on by default since the
last update) -- it isn't clear to what extent this may make the binary
packages different so precautionary revbumps will be coming in a
moment.

Technically for 92/93 the "gssapi" code could be attached to a
separate "gssapi" option so as to make the existing behavior entirely
unchanged, but this seems likely to be confusing in the long run and
thus not a good idea.