move get_ngraph_version_string() to a separate source file (#2087)

src/ngraph/runtime/cpu/CMakeLists.txt

@@ -110,6 +110,7 @@ set(SRC
     pass/cpu_rnn_fusion.cpp
     pass/cpu_workspace_insertion.cpp
     pass/cpu_reshape_sinking.cpp
+    ngraph_version.cpp
 )
 
 if (NOT NGRAPH_DEX_ONLY)

src/ngraph/runtime/cpu/cpu_backend.cpp

@@ -27,11 +27,6 @@
 using namespace ngraph;
 using namespace std;
 
-extern "C" const char* get_ngraph_version_string()
-{
-    return NGRAPH_VERSION;
-}
-
 extern "C" runtime::Backend* new_backend(const char* configuration_string)
 {
     // Force TBB to link to the backend

src/ngraph/runtime/cpu/ngraph_version.cpp

+//*****************************************************************************
+// Copyright 2017-2018 Intel Corporation
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//*****************************************************************************
+
+extern "C" const char* get_ngraph_version_string()
+{
+    return NGRAPH_VERSION;
+}