Rename BlobWriter to BlobBuilder

Make CompilerTestResources portable

Move all InternalsVisibleTo into the project files

More MSBuildTask cleanup

Use nameof instead of hardcoded argument names.

Added a document that lists some CodeGen differences.

This moves all of the InternalsVisibleTo which were defined in code into
the project files where the majority of the IVT definitions lived.

Add DiaSymReader.PortablePdb project to all solutions

BlobWrite clean up and tests

Add instructions for building csc with CscCore

Merge Portable PDB implementation into master

CscCore is the CoreCLR-compatible version of csc.exe. This change
adds support for building csc with CscCore by adding a no-op step
for analyzer loading, adding a script to copy over the CoreCLR runtime,
and adding instructions for using both of these together.

There is a number of known changes in the binaries produced for the same source code when compared to equivalent output of the old compiler. Some changes are improvements, some are bug fixes and some are indirect result of differences in implementation and emit strategies.

Most of the actual form and shape of emitted code is not a contract and compiler is only responsible for efficiently conveying the semantics of the original source. However there is enough interest in intentional changes here and it seems to be useful to have one place where some of the more significant changes are listed.

Lambda rewriter should rewrite method/property symbols when rewriting…

ReplaceSyntaxTree should throw on duplicate

...as AddSyntaxTrees does.

Defer building blob heap to metadata serialization phase

Move DeclTable diagnostics into parser

The errors being reported in the declaration table were inherently
syntactic and moving them into the parser eliminates some complexity.

Note: VB is not currently reporting
ERR_ReferenceDirectiveOnlyAllowedInScripts since it does not (yet)
lex/parse reference directives.

Update System.Reflection.Metadata to 1.1.0-alpha-00008

Since the containing type could have been changed if it is a type parameter in the containing method.

Fixes #3906

Clean up the MSBuild code

Fix a couple of issues:

- Use nameof where appropriate
- Accessibility should come before override

Plumb the features flag through our MSBuild and Workspaces layers.

closes #3879

Fix DataTips for parameterized property access...

(fixes #2602)