Fix xaccAccountGetBalanceAsOfDate() (bug #150757).

[Derek Atkins]

Log Message:
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Fix xaccAccountGetBalanceAsOfDate() (bug #150757).

	* src/engine/Account.c: fix xaccAccountGetBalanceAsOfDate() to properly
	  compute the balance at the end of the split list.  Fixes #150757.

Modified Files:
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    gnucash:
        ChangeLog
    gnucash/src/engine:
        Account.c