THRIFT-388. Create a "ONEWAY" message type that is an alias for "CALL"

Pave the way for a new message type for oneway function calls.
For now, just define the constant in all languages and make
server implementations treat it the same way as a normal call.
Only C++ and Erlang currently check the message type (on the
server side).

There is a little bit of redundancy in the Erlang code, but
the alternative is a bit gross, and this split-up will be
necessary eventually when we start handling one-way calls
differently.


git-svn-id: https://svn.apache.org/repos/asf/incubator/thrift/trunk@761389 13f79535-47bb-0310-9956-ffa450edef68
diff --git a/lib/cpp/src/protocol/TProtocol.h b/lib/cpp/src/protocol/TProtocol.h
index 37d0801..0c513d1 100644
--- a/lib/cpp/src/protocol/TProtocol.h
+++ b/lib/cpp/src/protocol/TProtocol.h
@@ -97,7 +97,8 @@
 enum TMessageType {
   T_CALL       = 1,
   T_REPLY      = 2,
-  T_EXCEPTION  = 3
+  T_EXCEPTION  = 3,
+  T_ONEWAY     = 4
 };
 
 /**