This patch is the next step towards (re)allowing fork/exec.

src/backend/access/transam/xlog.c

src/backend/bootstrap/bootstrap.c

src/backend/postmaster/pgstat.c

src/backend/postmaster/postmaster.c

src/backend/storage/buffer/buf_init.c

src/backend/storage/file/fd.c

src/backend/storage/freespace/freespace.c

src/backend/storage/ipc/ipci.c

src/backend/storage/ipc/pmsignal.c

src/backend/storage/ipc/shmem.c

src/backend/storage/ipc/sinvaladt.c

src/backend/storage/lmgr/lock.c

src/backend/storage/lmgr/lwlock.c

src/backend/storage/lmgr/proc.c

src/backend/tcop/postgres.c

src/include/access/xlogdefs.h

src/include/c.h

src/include/libpq/libpq-be.h

src/include/storage/fd.h

src/include/storage/ipc.h