title: RequiredMessage don't show in p:messages
body: <p>I'm trying to display a requiredMessage in p:messages but dont works. The p:messages just show the messages from BackingBean using addMessage().</p>
  
  <p>See:</p>
  
  <pre><code>&lt;p:messages globalOnly="true" autoUpdate="true" /&gt;
  &lt;h:form id="frmRegistro"&gt;
                  &lt;div class="form-group has-feedback"&gt;
                      &lt;h:inputText value="#{usuarioLogadoMB.newUser.nomeCompleto}"
                          styleClass="form-control" alt="Nome Completo"
                          pt:placeholder="Nome completo" /&gt;
                      &lt;span class="glyphicon glyphicon-user form-control-feedback"&gt;&lt;/span&gt;
                  &lt;/div&gt;
                  &lt;div class="form-group has-feedback"&gt;
                      &lt;h:inputText value="#{usuarioLogadoMB.newUser.email}" id="iptEmail"
                          required="true" requiredMessage="O email é obrigatório"
                          styleClass="form-control" alt="Email" pt:placeholder="Email" /&gt;
                      &lt;span class="glyphicon glyphicon-envelope form-control-feedback"&gt;&lt;/span&gt;
                  &lt;/div&gt;
                  &lt;div class="form-group has-feedback"&gt;
                      &lt;h:inputSecret value="#{usuarioLogadoMB.newUser.senha}"
                          required="true" requiredMessage="A senha é obrigatória"
                          styleClass="form-control" alt="Senha" pt:placeholder="Senha" /&gt;
                      &lt;span class="glyphicon glyphicon-lock form-control-feedback"&gt;&lt;/span&gt;
                  &lt;/div&gt;
                  &lt;div class="form-group has-feedback"&gt;
                      &lt;h:inputSecret value="#{usuarioLogadoMB.newUser.confirmacaoSenha}"
                          required="true"
                          requiredMessage="A confirmação da senha é obrigatória"
                          styleClass="form-control" alt="Repita a senha"
                          pt:placeholder="Repita a senha" /&gt;
                      &lt;span class="glyphicon glyphicon-log-in form-control-feedback"&gt;&lt;/span&gt;
                  &lt;/div&gt;
                  &lt;div class="row"&gt;
                      &lt;div class="col-xs-4"&gt;
                          &lt;h:commandButton action="#{usuarioLogadoMB.concluirRegistro()}"
                              value="Registrar" styleClass="btn btn-primary btn-block btn-flat" /&gt;
                      &lt;/div&gt;
                      &lt;!-- /.col --&gt;
                  &lt;/div&gt;
              &lt;/h:form&gt;
  </code></pre>
  
  <p>If i put p:message with for attribute to each component the message is showed inline, but i want to use the p:messages to avoid add p:message to each component.</p>