This removes the majority of references to the deprecated Desktop
assemblies.  The only remaining ones are in the VSIX projects.  They
must remain until we actually delete the assemblies.

Fixes #2604.

VB EnC: when lowering conditional branches produce a pattern that allows the debugger to perform function remapping

Enable Conditional Access optimizations for cases when LocalRewriter introduces a local in the process of initial lowering of the access.

Fixed #2424.

This test was disabled due to an issue running the test on CTP6.  This issue no longer reproduces on
newer builds including the RC.  Enabling and closing the bug.

closes #856

Fixes #564

Fixes #1958
Closes #1967 (a good year)

Fixes #2094.

Upgrades System.Collections.Immutable to 1.1.34-rc and
System.Reflection.Metadata to 1.0.19-rc.

Fix DiagnosticAnalyzerExtensions.GetDiagnosticAnalyzerCategory to return DiagnosticAnalyzerCategory.SemanticDocumentAnalysis if the analyzer has semantic actions and cannot support semantic span based analysis.

Fixes #1709

Adjust implementation of SourceNamespaceSymbol.IsDefinedInSourceTree to account for the fact that constituents of a root namespace are implicitly defined in every syntax tree and, therefore, should be visited for the purpose of collecting diagnostics within a syntax tree. Without this, an unexpected “unnecessary imports” diagnostic could be reported for a syntax tree and some expected diagnostics could remain unreported for the tree.

This change is related to issue #377. It looks like original repro was addressed in commit 755ffcd0, but there was a mistake around handling method calls.

Closes #1511

Fixes #1312

Binary serialization is not supported in CoreCLR and hence must be removed
from the subset which runs there.  This code is only used to support
CodeLens so rather than moving it around we are simply removing it
completely.  It will be relocated to CodeLens internally to continue supporting
their scenarios.

The Public API changes to DocumentId and ProjectId were necessary to
continue supporting serialization outside of the Roslyn code base.

closes #915

1. NotConfigurable diagnostic shouldn't be reported if it is disabled (fixes #1473)
2. NotConfigurable enabled diagnostics implies analyzer is never suppressed. NotConfigurable disable diagnostics shouldn't participate in deciding whether or not analyzer is suppressed.

Conditional Access receiver wasn’t properly captured allowing for the
receiver to be changed between a null check and the access.

Now that the comment formatting issue is fixed in the Formatter type, we can run the formatter on the remainder of the VB code base.

closes #1424

Fixes #252 : If an analyzer reports a diagnostic with an unsupported diagnostic ID, i.e. no descriptor returned by SupportedDiagnostics has that ID, then throw an ArgumentException in ReportDiagnostic method. This exception would be turned into an analyzer diagnostic by the driver and reported back to the analyzer host.
Also fix a few tests that were reporting diagnostics with unsupported ID!

Changes to the syntax associated with BoundQueryBody caused slight changes in error span of some rarely reported errors. Update tests.

Fixes #1099

Fixes #1028
Closes #1116