pgsql: Backpatch reservation of shared memory region during backend

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

The same functionality has been in 8.3 and 8.4 for almost a year, and seems
to have solved some of the more common shared memory errors on Windows.

Tags:
----
REL8_2_STABLE

Modified Files:
--------------
    pgsql/src/backend/port:
        sysv_shmem.c (r1.47.2.2 -> r1.47.2.3)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/port/sysv_shmem.c?r1=1.47.2.2&r2=1.47.2.3)
    pgsql/src/backend/port/win32:
        shmem.c (r1.13.2.1 -> r1.13.2.2)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/port/win32/shmem.c?r1=1.13.2.1&r2=1.13.2.2)
    pgsql/src/backend/postmaster:
        postmaster.c (r1.505.2.8 -> r1.505.2.9)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/postmaster/postmaster.c?r1=1.505.2.8&r2=1.505.2.9)
    pgsql/src/include/port:
        win32.h (r1.63.2.3 -> r1.63.2.4)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/include/port/win32.h?r1=1.63.2.3&r2=1.63.2.4)