pgsql: Reserve the shared memory region during backend startup on

Log Message:
-----------
Reserve the shared memory region during backend startup on Windows, so
that memory allocated by starting third party DLLs doesn't end up
conflicting with it.

Hopefully this solves the long-time issue with "could not reattach
to shared memory" errors on Win32.

Patch from Tsutomu Yamada and me, based on idea from Trevor Talbot.

Tags:
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REL8_4_STABLE

Modified Files:
--------------
    pgsql/src/backend/port:
        win32_shmem.c (r1.11 -> r1.11.2.1)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/port/win32_shmem.c?r1=1.11&r2=1.11.2.1)
    pgsql/src/include/port:
        win32.h (r1.88 -> r1.88.2.1)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/port/win32.h?r1=1.88&r2=1.88.2.1)
    pgsql/src/backend/postmaster:
        postmaster.c (r1.583.2.2 -> r1.583.2.3)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/postmaster/postmaster.c?r1=1.583.2.2&r2=1.583.2.3)