[except.terminate] Add contract violation with continuation mode off

Author: jensmaurer

source/exceptions.tex

@@ -1039,6 +1039,10 @@
 for a failed contract condition check\iref{dcl.attr.contract}
 on a \tcode{noexcept} function exits via an exception, or
 
+\item%
+when the violation handler has completed after a failed contract check
+and the continuation mode is \term{off}, or
+
 \item%
 when a
 \grammarterm{throw-expression}\iref{expr.throw}