Added SCO support, from Daniel Harris.

src/backend/commands/vacuum.c

src/backend/executor/execScan.c

src/backend/executor/nodeHash.c

src/backend/executor/nodeHashjoin.c

src/backend/executor/nodeTee.c

src/backend/libpq/pqcomm.c

src/backend/storage/buffer/buf_init.c

src/backend/storage/buffer/bufmgr.c

src/backend/storage/buffer/localbuf.c

src/backend/storage/file/fd.c

src/backend/storage/large_object/inv_api.c

src/backend/tcop/postgres.c

src/backend/utils/Gen_fmgrtab.sh.in

src/backend/utils/adt/float.c

src/backend/utils/adt/misc.c

src/backend/utils/cache/relcache.c

src/configure

src/configure.in

src/template/.similar

src/utils/version.c