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_3_STABLE

Modified Files:
--------------
    pgsql/src/backend/port:
        win32_shmem.c (r1.4.2.4 -> r1.4.2.5)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/port/win32_shmem.c?r1=1.4.2.4&r2=1.4.2.5)
    pgsql/src/include/port:
        win32.h (r1.83 -> r1.83.2.1)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/port/win32.h?r1=1.83&r2=1.83.2.1)
    pgsql/src/backend/postmaster:
        postmaster.c (r1.551.2.2 -> r1.551.2.3)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/postmaster/postmaster.c?r1=1.551.2.2&r2=1.551.2.3)