Fix OptionsPanel leaks and API change

vsintegration/src/FSharp.Editor/Common/FSharpOptionsPanels.fs

@@ -41,8 +41,12 @@ type FSharpSettingsPanel() =
         widget.EntryCompilerPath.Text <- if use_default || prop_compiler_path = "" then default_compiler_path else prop_compiler_path
         widget.EntryCompilerPath.Sensitive <- not use_default
 
-    override x.Dispose() =
-        if widget <> null then widget.Dispose()
+    override x.Dispose (disposing:bool) =
+        if widget <> null then
+            widget.Dispose()
+            widget <- null
+
+        base.Dispose (disposing)
 
     override x.CreatePanelWidget() =
         widget <- new FSharpSettingsWidget()
@@ -118,11 +122,16 @@ type CodeGenerationPanel() =
         | 3 -> "Itanium"
         | _ -> "anycpu"
 
-    override x.Dispose () =
+    override x.Dispose (disposing:bool) =
         if widget <> null then
             widget.Dispose ()
+            widget <- null
+
         if debugCheckedHandler <> null then
             debugCheckedHandler.Dispose()
+            widget <- null
+
+        base.Dispose(disposing) 
 
     override x.CreatePanelWidget() =
         widget <- new FSharpCompilerOptionsWidget ()