Imported Upstream version 4.3.2.467

Former-commit-id: 9c2cb47f45fa221e661ab616387c9cda183f283d

external/referencesource/System.Web/Util/versioninfo.cs

@@ -79,7 +79,12 @@ namespace System.Web.Util {
 
         internal static string SystemWebVersion {
             get {
-                return ThisAssembly.InformationalVersion;
+
+                // Previously this represented the File version of mscorlib.dll.  Many other libraries in the framework and outside took dependencies on the first three parts of this version 
+                // remaining constant throughout 4.x.  From 4.0 to 4.5.2 this was fine since the file version only incremented the last part.  Starting with 4.6 we switched to a file versioning
+                // scheme that matched the product version.  In order to preserve compatibility with existing libraries, this needs to be hard-coded.
+
+                return "4.0.30319.42000";
             }
         }