pgsql: Native shared memory implementation for win32.

Log Message:
-----------
Native shared memory implementation for win32.
Uses same underlying tech as before, but not the sysv emulation layer.

Modified Files:
--------------
    pgsql:
        configure (r1.535 -> r1.536)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/configure.diff?r1=1.535&r2=1.536)
        configure.in (r1.502 -> r1.503)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/configure.in.diff?r1=1.502&r2=1.503)
    pgsql/src/backend/port:
        sysv_shmem.c (r1.49 -> r1.50)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/port/sysv_shmem.c.diff?r1=1.49&r2=1.50)
    pgsql/src/backend/port/win32:
        Makefile (r1.9 -> r1.10)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/port/win32/Makefile.diff?r1=1.9&r2=1.10)
    pgsql/src/tools/msvc:
        Mkvcbuild.pm (r1.3 -> r1.4)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/tools/msvc/Mkvcbuild.pm.diff?r1=1.3&r2=1.4)

Added Files:
-----------
    pgsql/src/backend/port:
        win32_shmem.c (r1.1)

(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/port/win32_shmem.c?rev=1.1&content-type=text/x-cvsweb-markup)

Removed Files:
-------------
    pgsql/src/backend/port/win32:
        shmem.c
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/port/win32/shmem.c)