More fixes as a result of testing.

More fixes as a result of testing.

Testing voiding of lost on claims returned turned up a problem with
double voiding the same bill when/if the claims returned copy is
later checked in.  The fix is to modify CircCommon::void_bills_of_type
so that it does not void already voided bills.

Also, the BILL_ALREADY_VOIDED event was not getting propagated to the
staff client, so we changed CircCommon::real_void_bills to add the
event to the editor.

Finally, there was a typo in the original event description in
ils_events.xml, so we altered that language to be simpler English.

Signed-off-by: Jason Stephenson <jason@sigio.com>