fix nulll exception in unused declaration analyzer

Check the CancellationToken in the DeclarePublicAPI analyzer

Restore some access suppression tests in the binder needed for EE

Fixes a few test failures.

Fix a bug in AnalyzerManager.GetCompilationAnalysisScopeCoreAsync

Fix a bug in AnalyzerManager.GetCompilationAnalysisScopeCoreAsync to use the GetOrAdd overload that takes a Func rather then value. This should avoid spawing multiple tasks to execute CompilationStartAction for an analyzer, and fix the VS responsiveness issues we have been seeing in DeclarePublicAPIAnalyzer.

Related to issue #610.

The DeclarePublicAPI analyzer loops over the set of AdditionalFiles
looking for one named "PublicAPI.txt", and later loops through all the
lines in that file. If there are a large number of AdditionalFiles, or
the file contains a large number of lines (which is certainly the case
for some of our projects) we may end up doing a lot of work even after
analysis has been cancelled.

This can happen during typing, where we may repeatedly cancel analysis
and start again as the user is typing. We can potentially end up with a
bunch of Tasks doing long-running but unnecessary work, consuming system
resources and making VS less responsive.

The fix here is to be aggressive about checking the CancellationToken
while in these loops.

Added “SemanticModel.WithSuppressAccessChecks” extension method.

Handle OperationCanceledException in AnalyzerManager (CR feedback from Jason)

Handle TaskCancelledException in AnalyzerManager.GetAnalyzerActionsAsync

add support for error list IsStable - progress indicator

Use ReportFatalError in TaskFactory helpers

Handle failing conversion in synthesized code

cleaned code little bit based on PR feedback

AnalyzerManager maintains a cache of per-analyzer tasks to compute sessions and compilation analyis scopes. If multiple clients simultaneously ask for the analyzer actions for a given analyzer, then all of them receive the same task. If the thread that created this task is now cancelled, all other clients get a TaskCancelledException with a different cancellation token then theirs and the exception goes unhandled, bringing down VS.

Fix is to catch this task cancelled exception in AnalyzerManager, remove the entry for the the cancelled task in the scope map and then re-attempt computing scope, if our cancellelation has not fired.

Add options to FakeSign.exe
-u (unsign) reverses the default behavior by clearing the strong name signed bit.
-f (force) forces an update even if it would change nothing.

Don't allow -f to be used on assemblies that aren't managed.

Support setting the active rule set from Solution Explorer

Add the -f (force) option to force an update even if the file would
otherwise not be modified.

Add usage information for the "-u" option.

Use ternaries inside interpolated strings for error messages.

Add documentation clarifying C# compiler behavior for static types

Automated checkin: update Concord binaries from \\cpvsbuild\drops\dev14\VSPro_1\raw\22617.00 to version 22618.00.

Move enforcement of "no static type as type argument" to constraint validation

related to #324

Start Documentation for Compiler Specification

first working version. need some more tweaks.