Remove compile time transport interface switch

- Remove the compile time check of the transport implementation.
  The transport (zeromq/nanomsg) can be chosen at run time with:
  `device.SetTransport("zeromq"); // possible values are "zeromq" and "nanomsg"`.

  For devices that use FairMQProgOptions, the transport can be configured via cmd option:
  `--transport zeromq` or `--transport nanomsg`. Default values is "zeromq".
  The device receives the configured value with:
  `device.SetTransport(config.GetValue<std::string>("transport"));`

  Old method of setting transport still works. But the NANOMSG constant is not defined.

- Remove old `fairmq/prototest` directory. It was only used as a test for protobuf.
  The protobuf part of Tutorial3 does the same (with different values).

- Fix a bug in FairMQPollerNN, where the `revents` value was not initialized.
  This caused the `poller->CheckOutput()` to trigger when it should not.

examples/MQ/6-multiple-channels/CMakeLists.txt

@@ -10,6 +10,8 @@ configure_file(${CMAKE_SOURCE_DIR}/examples/MQ/6-multiple-channels/ex6-multiple-
 
 Set(INCLUDE_DIRECTORIES
   ${CMAKE_SOURCE_DIR}/fairmq
+  ${CMAKE_SOURCE_DIR}/fairmq/zeromq
+  ${CMAKE_SOURCE_DIR}/fairmq/nanomsg
   ${CMAKE_SOURCE_DIR}/fairmq/devices
   ${CMAKE_SOURCE_DIR}/fairmq/tools
   ${CMAKE_SOURCE_DIR}/fairmq/options
@@ -19,28 +21,10 @@ Set(INCLUDE_DIRECTORIES
 
 Set(SYSTEM_INCLUDE_DIRECTORIES
   ${Boost_INCLUDE_DIR}
+  ${ZMQ_INCLUDE_DIR}
+  ${NANOMSG_INCLUDE_DIR}
 )
 
-If(NANOMSG_FOUND)
-  Set(INCLUDE_DIRECTORIES
-    ${INCLUDE_DIRECTORIES}
-    ${CMAKE_SOURCE_DIR}/fairmq/nanomsg
-  )
-  Set(SYSTEM_INCLUDE_DIRECTORIES
-    ${SYSTEM_INCLUDE_DIRECTORIES}
-    ${ZMQ_INCLUDE_DIR}
-  )
-Else(NANOMSG_FOUND)
-  Set(INCLUDE_DIRECTORIES
-    ${INCLUDE_DIRECTORIES}
-    ${CMAKE_SOURCE_DIR}/fairmq/zeromq
-  )
-  Set(SYSTEM_INCLUDE_DIRECTORIES
-    ${SYSTEM_INCLUDE_DIRECTORIES}
-    ${ZMQ_INCLUDE_DIR}
-  )
-EndIf(NANOMSG_FOUND)
-
 Include_Directories(${INCLUDE_DIRECTORIES})
 Include_Directories(SYSTEM ${SYSTEM_INCLUDE_DIRECTORIES})