message: Fix crash caused by an unsigned overflow.
  Thanks to Joseph Bisch for discovery.
  This was an artifact of converting ZNC to use CMessage. Released
  versions are not affected.
diff: @@ -1320,7 +1320,7 @@ void CIRCSock::ReachedMaxBuffer() {
  void CIRCSock::ParseISupport(const CMessage& Message) {
  const VCString vsParams = Message.GetParams();
  - for (size_t i = 1; i < vsParams.size() - 1; ++i) {
  + for (size_t i = 1; i + 1 < vsParams.size(); ++i) {
  const CString& sParam = vsParams[i];
  CString sName = sParam.Token(0, false, "=");
  CString sValue = sParam.Token(1, true, "=");
  