[Stabilization] Don't crash when we hear about very stale diagnostics for our current Document.

Unix Mono change

[AskMode] Make all operations in Paste a single undo transaction

[AskMode] Add a command handler for pasting from interactive window

Since it is handled by `CreateAndActivateBuffer` already. And a new UndoManager is not created
by calling `GetTextBufferUndoManager` in `AddLanguageBuffer`, it was created in `CreateAndActivateBuffer`
as well, we just retrive that one here.

Conflicts:
	src/EditorFeatures/Core/EditorFeaturesResources.resx

Final changes to the Scripting public API

Support "Go to next/previous method" commands

1. Ensure the destination is visible and not collapsed.
2. Disable in contained documents (as in VS2013)
3. Handle being outside any method level member
4. Add tests for VB.
5. Add tests for script.

Conflicts:
	src/EditorFeatures/TestUtilities/Traits.cs

Conflicts:
	src/EditorFeatures/Core/EditorFeatures.csproj

Fix VB incorrectly reported redundant casts in compound assignment statements

Also add unti test.