Frederic Leroy's patch (#314512) to add a close box to each notebook

[David Hampton]

Log Message:
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Frederic Leroy's patch (#314512) to add a close box to each notebook
tab.  Enhanced to make the tab visibility a user preference.

Tags:
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gnucash-gnome2-dev

Modified Files:
--------------
    gnucash:
        ChangeLog
    gnucash/src/gnome/schemas:
        apps_gnucash_general.schemas
    gnucash/src/gnome-utils:
        gnc-main-window.c
        preferences.glade