Remove the remnants of the gtk1/gnome1 MDI code.

[David Hampton]

Log Message:
-----------
Remove the remnants of the gtk1/gnome1 MDI code.

Tags:
----
gnucash-gnome2-dev

Modified Files:
--------------
    gnucash/src/gnome:
        gnc-plugin-page-account-tree.c
        gw-gnc-spec.scm
        top-level.c
    gnucash/src/gnome-utils:
        Makefile.am
        gnc-main-window.c
        gnc-window.c
        gw-gnome-utils-spec.scm
    gnucash/src/report/report-gnome:
        window-report.h
    gnucash/src/report/report-system:
        report-utilities.scm
    gnucash/src/scm:
        main-window.scm

Removed Files:
-------------
    gnucash/src/gnome-utils:
        gnc-mdi-utils.c
        gnc-mdi-utils.h