Improvement of PR#89 - Bug 781711: Add reversing transaction definition

From the comment in the PR.

Author: sunfish62

guide/C/gnc-glossary.xml

@@ -331,9 +331,11 @@
    <glossdef>
       <para>In formal accounting, a transaction is never deleted. Therefore, when
          a mistake is made, the original transaction remains in the ledger, and a
-         transaction is added to the ledger that reverses the original. This
-         <emphasis>reversing transaction</emphasis> restores the books to the state before
-         the error, and a new correct transaction is created. Reversing
+         transaction is added to the ledger that reverses the original. This 
+         <emphasis>reversing transaction</emphasis> duplicates the original transaction, 
+         but with debit and credit amounts reversed. This removes the effect of the 
+         erroneous transaction from the books. After entering the reversing transaction, 
+         a corrected transaction can then be entered. Reversing
          transactions are not commonly used in personal accounting.</para>
    </glossdef>
 </glossentry>