Revert "IVGCVSW-2056 + IVGCVSW-2064 : move ClContextControl to the ClBackend"

This reverts commit d4dfa684941a21314b70593d01b0fc2167eebad4.

Change-Id: Id61ce69215505c3cf5d30ec2a7ec9127fb2554fc
diff --git a/src/backends/reference/RefBackend.cpp b/src/backends/reference/RefBackend.cpp
index 91fc3c9..b6fb0ff 100644
--- a/src/backends/reference/RefBackend.cpp
+++ b/src/backends/reference/RefBackend.cpp
@@ -9,6 +9,8 @@
 
 #include <backendsCommon/BackendRegistry.hpp>
 
+#include <boost/cast.hpp>
+
 namespace armnn
 {
 
@@ -19,7 +21,7 @@
 {
     BackendRegistryInstance(),
     RefBackend::GetIdStatic(),
-    [](const EmptyInitializer&)
+    []()
     {
         return IBackendInternalUniquePtr(new RefBackend);
     }