Remove BEOS port.

configure

configure.in

doc/src/sgml/installation.sgml

doc/src/sgml/runtime.sgml

src/Makefile.shlib

src/backend/main/main.c

src/backend/port/Makefile

src/backend/port/beos/Makefile

src/backend/port/beos/sem.c

src/backend/port/beos/shm.c

src/backend/port/beos/support.c

src/backend/port/dynloader/beos.c

src/backend/port/dynloader/beos.h

src/backend/postmaster/fork_process.c

src/backend/storage/lmgr/proc.c

src/backend/tcop/postgres.c

src/backend/utils/init/miscinit.c

src/bin/initdb/initdb.c

src/bin/pg_ctl/pg_ctl.c

src/bin/pg_resetxlog/pg_resetxlog.c