John Ellson's patch to fix some gcc4 warnings (bug #162582).

[Derek Atkins]

Log Message:
-----------
John Ellson's patch to fix some gcc4 warnings (bug #162582).

Modified Files:
--------------
    gnucash:
        ChangeLog
    gnucash/src/backend/file/test:
        test-string-converters.c
    gnucash/src/engine:
        gnc-numeric.c
        kvp_frame.c
    gnucash/src/engine/test:
        test-book-merge.c
    gnucash/src/gnome:
        gnc-split-reg.c
        mainwindow-account-tree.c
    gnucash/src/gnome-utils:
        gnc-account-sel.c
        gnc-amount-edit.c
        gnc-date-delta.c
        gnc-date-edit.c
        gnc-date-format.c
        gnc-dense-cal.c
        gnc-frequency.c