Prepare PR's for the next release of the F# SDK

[KevinRansom]

/cc @dsyme @PatrickMcDonald @saul @mjmckp @0x53A @OnurGumus @liboz @jack-pappas @manofstick

VS 2017.6 will include an version number FSharp.Core revision and so we are able to add new API's to it.

This list of PR's need attention:

Please review, comment, fix merge conflicts, or let me know to consider them for the next update.

If the changes are approved and green by January then they will be in. Any that go green after that will be subject to our ability to negotiate with ship room.

==================================================================

[WIP, FS-1042] Implement transpose on Seq, List and Array #4020

[FS-1041] Add IReadOnlyCollection/List/Dictionary implementations to FSharp.Core collections
#4014
Add NativePtr.toByRef
#3691

[RFC Needed] F# 4.x: Add ToFSharpFunc overloads for Func<...>, especially for .NET Core
#3013

[FS-1028] - Implement Async.StartImmediateAsTask
#2534

[FS-1041] Add System.Collections.ICollection implementations to F# set/map
#2085

==================================================================

[cartermp]

@KevinRansom A number of these PRs are language features and not additions to FSharp.Core. As per our conversation yesterday, we are revving the F# SDK, not the F# language. The following PRs are cut out of this by that definition:

• [WIP] Virtual Tags for Discriminated Unions #1517
• [FS-1037] Allow Union Constructor to deal with Flexible Types #2382
• [FS-1030] - Anonymous records #2671
• Additional comments and testing related to SRTP resolution #3967
• [RFC Needed] better warnings on mutable struct #3968

[dsyme]

@cartermp I've removed those from the list

[cartermp]

Closing as #3013 and #2085 did not make the cut