VS: Factor out Visual Studio Version enumeration

Source/CMakeLists.txt

@@ -975,6 +975,7 @@ if(WIN32)
         cmVisualStudioWCEPlatformParser.cxx
         cmVSSetupHelper.cxx
         cmVSSetupHelper.h
+        cmVSVersion.h
       )
 
     # Add a manifest file to executables on Windows to allow for

Source/cmGlobalVisualStudioGenerator.h

@@ -14,6 +14,7 @@
 
 #include "cmGlobalGenerator.h"
 #include "cmTargetDepend.h"
+#include "cmVSVersion.h"
 #include "cmValue.h"
 
 class cmCustomCommand;
@@ -31,15 +32,7 @@ class cmake;
 class cmGlobalVisualStudioGenerator : public cmGlobalGenerator
 {
 public:
-  /** Known versions of Visual Studio.  */
-  enum class VSVersion : uint16_t
-  {
-    VS14 = 140,
-    VS15 = 150,
-    VS16 = 160,
-    VS17 = 170,
-    VS18 = 180,
-  };
+  using VSVersion = cm::VS::Version;
 
   ~cmGlobalVisualStudioGenerator() override;
 

Source/cmVSVersion.h

@@ -0,0 +1,19 @@
+/* Distributed under the OSI-approved BSD 3-Clause License.  See accompanying
+   file LICENSE.rst or https://cmake.org/licensing for details.  */
+#pragma once
+
+#include <cstdint>
+
+namespace cm {
+namespace VS {
+/** Known versions of Visual Studio.  */
+enum class Version : std::uint16_t
+{
+  VS14 = 140,
+  VS15 = 150,
+  VS16 = 160,
+  VS17 = 170,
+  VS18 = 180,
+};
+}
+}