Conflicts:
	src/Compilers/CSharp/Test/Semantic/Semantics/NullableReferenceTypesTests.cs

* Call this.DeclaringCompilation.EnsureReadOnlyAttributeExists() when needed

* Promote EmbeddedAttribute to be used by both compilers

* Generate Embedded attributes on PE Module Builder

* Thread PEModuleBuilder through Symbol.AddSynthesizedAttributes()

* Fix failing tests

* Base case passing

* Refactor ReadOnlyAttribute to IsReadOnlyAttribute

* Fix build break

* More Tests

* Clean up

* PR Comments #1

PR Comments #3

PR Comments #4

PR Comments #5

PR Comments #6

PR Comments # 7

* Handle NoPIA

Added more tests

* Lambdas and Local functions no longer generate attributes in symbols

Added tests for constructors and operators

Signal need for synthesized attributes in local rewriter for lambdas an local functions

Clean up

* Clean up

* More PR Feedback

* Adding more tests

* More PR Comments

* More tests for explicit interface implementations

* Latest PR Comments

* Moved EnsureIsReadOnlyAttributeExists to AfterAddingTypeMembersChecks

* Fix failing tests

Fixes #7659.

Fixes #4163.

Splits Microsoft.CodeAnalysis, Microsoft.CodeAnalysis.CSharp and Microsoft.CodeAnalysis.VisualBasic into portable and desktop assemblies.

Existing Core\Source, CSharp\Source and VisualBasic\Source directories are renamed to Core\Portable, CSharp\Portable and VisualBasic\Portable.
New sibling Desktop folders are added and non-portable source is moved there.
"System.Runtime" references has to be removed in order for the portable project system magic to automatically add facade references.
 (changeset 1281686)

 (changeset 1279398)

Public API Change: Rename IFieldSymbol.AssociatedPropertyOrEvent , IMethodSymbol.AssociatedPropertyOrEvent and INamedTypeSymbol. AssociatedEvent APIs to AssociatedSymbol to accommodate for future language changes. (changeset 1210026)