Fix leap-year computation in the 'last_mday' computation.

[Derek Atkins]

Log Message:
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Fix leap-year computation in the 'last_mday' computation.

	* src/engine/date.c: Fix the last-day-of-month computation for
	  leap years.  Need to use modulo, not divide.  (Patch by
	  Neil Williams.

Tags:
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gnucash-1-8-branch

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