Move slock_t typdefs into s_lock.h from include/port files for

src/backend/port/dynloader/netbsd.c

src/backend/port/dynloader/openbsd.c

src/backend/storage/lmgr/s_lock.c

src/backend/storage/lmgr/spin.c

src/include/port/aix.h

src/include/port/beos.h

src/include/port/bsdi.h

src/include/port/cygwin.h

src/include/port/darwin.h

src/include/port/freebsd.h

src/include/port/hpux.h

src/include/port/irix5.h

src/include/port/linux.h

src/include/port/netbsd.h

src/include/port/nextstep.h

src/include/port/openbsd.h

src/include/port/osf.h

src/include/port/qnx4.h

src/include/port/sco.h

src/include/port/solaris.h