AIX - pgport/contrib resolution

The comment in regress/GNUmakefile about the pgport symbols not being
found got me thinking about why that might be the case.

I finally noticed that when we are building the postgres.imp file, we
are not pulling in the pgport symbols, since they are not being linked
into the local SUBSYS.o before running mkldexport.sh.

I noticed that windows has a similar dilemma when creating the .def
file.

The solution was to suck in libpgport.a before we extract all the
symbols out.

A patch to that affect is attached.

backend/Makefile - fix rule for AIX regarding pgport files
port/getopt_long - needed to have optreset wrapped in HAVE_INT_OPTRESET
regress/GNUmakefile - hopefully I backed out the change to bring in
pgsleep well enough

With these changes in place, I was able to complete a full build and
test suite (including contrib).

Thanks,
-rocco