Send an 'invoice modified' event when a payment is applied (#139092).

[Derek Atkins]

Log Message:
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Send an 'invoice modified' event when a payment is applied (#139092).

	* src/business/business-core/gncInvoice.c:
	  send an event when a payment is processed so the invoice gets
	  updated as "paid" in the search window.
	  Fixes #139092.

Tags:
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gnucash-1-8-branch

Modified Files:
--------------
    gnucash:
        ChangeLog
    gnucash/src/business/business-core:
        gncInvoice.c