Some remaining htonl() and ntohl() calls in the code

Hi all,

Since 510b8cbf, we have in-core equivalents for htonl(), ntohl() & co
through pg_bswap.h that allows to compile with a built-in function if
the compiler used has one.

All the existing calls in the code tree have been changed with
0ba99c84 for performance reasons (except the libpq examples), however
the FE/BE code of GSSAPI encryption code did not get this call in
b0b39f7.  I think that we had better switch to the built-ins functions
as well for this case.  The argument of consistency matters here, but
also perhaps the argument of performance, where it may not be easy to
measure a difference.

Attached is a patch to do the switch.  None of the files changed
include arpa/inet.h.  Any thoughts?

Thanks,
--
Michael