Add no-route constant to spec file

The no-route constant is documented in our website:

https://rabbitmq.com/amqp-0-9-1-reference.html#constants

However, it was missing in the XML spec file, and it was not getting
generated with Apigen program.

Signed-off-by: Aitor Perez Cedres <[email protected]>

Author: Zerpet

projects/Unit/APIApproval.Approve.verified.txt

@@ -146,6 +146,7 @@ namespace RabbitMQ.Client
         public const int InternalError = 541;
         public const int InvalidPath = 402;
         public const int NoConsumers = 313;
+        public const int NoRoute = 312;
         public const int NotAllowed = 530;
         public const int NotFound = 404;
         public const int NotImplemented = 540;

projects/specs/amqp0-9-1.stripped.xml

@@ -34,6 +34,7 @@ THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
   <constant name="frame-end" value="206"/>
   <constant name="reply-success" value="200"/>
   <constant name="content-too-large" value="311" class="soft-error"/>
+  <constant name="no-route" value="312" class="soft-error"/>
   <constant name="no-consumers" value="313" class="soft-error"/>
   <constant name="connection-forced" value="320" class="hard-error"/>
   <constant name="invalid-path" value="402" class="hard-error"/>

projects/specs/amqp0-9-1.xml

@@ -187,6 +187,13 @@
     </doc>
   </constant>
 
+  <constant name = "no-route" value = "312" class = "soft-error">
+    <doc>
+      Returned when RabbitMQ sends back with 'basic.return' when a 'mandatory'
+      message cannot be delivered to any queue.
+    </doc>
+  </constant>
+
   <constant name = "no-consumers" value = "313" class = "soft-error">
     <doc>
       When the exchange cannot deliver to a consumer when the immediate flag is