More performance improvements 

Re-enable tests that are skipped.

RE: Issue #686 - Bitwise Not does not trigger IntelliSense

Fixes: https://github.com/dotnet/roslyn/issues/686

BeginAsyncOperation got optional parameters for debuggability including
[CallerFileName] and [CallerLineNumber] arguments, but our mocks were
not specifying them.

Fixes most of #9873.

Adress flakiness in TestTagsChangedForEntireFile

Fix building with non-Visual Studio 2015

Merge stabilization into master

This hopefully fixes #9723, because there won't be the chance that the
WorkspaceRegistrationChanged event will fire *after* the first TagsChanged
instead of before.

I'm unable to figure out what is going wrong here. My best guess is that
a second workspace event happens before the text changes that causes
classification to refresh while still on the original snapshot.

This adds some additional diagnostics to our test to try to identify that.

Also changes CheckPoint.Release to CheckPoint.TryRelease, so that it's
possible to observe if someone else already caused the checkpoint task to
complete.

Related to #9723.

Reenable the CurrentWorkingDirectory test

We conditionally add this in a target to work around Visual Studio's
poor handling of conditions on Reference nodes in the project system.

In future versions of Shell.14.0, some types have been type forwarded
to this assembly. This means we'll take a reference to Immutable.14.0
when building with 14.0, but that's fine since we won't use it.

Add version variables for Esent, Elfie and InteractiveWindow

Revert "Revert "Merge pull request #6636 from CyrusNajmabadi/asyncLazy""

Fix unit test deadlocks

Fix the MSBuild warning check

More refactorings in Perf Test tool

There are runs on Jenkins where the IDE is failing the assertions of running on the foreground / background thread.  This causes an exception to be emitted and generally fails the resulting test.  In the case of this bug though the exception was causing the test to deadlock due to this particular call.

http://source.roslyn.io/#Microsoft.CodeAnalysis.EditorFeatures/Implementation/Classification/SyntacticClassificationTaggerProvider.TagComputer.cs,203

``` csharp
_notificationService.RegisterNotification(() =>
    {
        _workQueue.AssertIsForeground();
        ReportChangedSpan(snapshot.GetFullSpan());
    },
    ReportChangeDelayInMilliseconds,
    _listener.BeginAsyncOperation("ReportEntireFileChanged"),
    _reportChangeCancellationSource.Token);
```

Here the callback throws due to the failed foreground check.  The implementation of RegisterNotification wasn't properly hardened to ensure `IAsyncToken` was disposed in the face of an exception.  This caused that particular token to never complete and deadlocked the unit tests.

closes #7825

Work around MSBuild race condition

Enc: async/iterator editing regression fix

Make compiler VSIX extension aware of VS versions

Prepare cibuild.cmd to receive /buildTimeLimit

The compiler was hard coding the version of MSBuild to be 14.0.  This works on Dev14 but fails in Dev15 where MSBuild is 15.0.  This changes the extension to pick the MSBuild version based on the current version of Visual Studio.

Misc Perf cleanup