Convert the multiple choice option from using the deprecated

[David Hampton]

Log Message:
-----------
Convert the multiple choice option from using the deprecated
GtkOptionMenu widget to using a GtkComboBox widget.  Fix some warnings
when using a currency option.  Make the account list option expand to
fill available space.

Tags:
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gnucash-gnome2-dev

Modified Files:
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    gnucash:
        ChangeLog
    gnucash/src/gnome-utils:
        dialog-options.c