Change download URL for PCL reference assemblies

Bump NuGetSdkResolver in msbuild

Backport fixes for sharing wrappers when type attributes are involved (…

…mono#21537)

* [wasm] Fix the handling of i8/u8 in get_wrapper_shared_type_full (). (mono#19859)

Previously, these were returned verbatim, which caused sharing issues when the type had
attributes.

Fixes mono#19841.

* [aot] Fix the handling of r4/r8 parameter types with attributes during generic sharing. (mono#20217)

The attributes need to be ignored as with the other types, otherwise gsharedvt wrappers for signatures with
parameters like double f = default will not be found.

Fixes mono#20195.

Co-authored-by: Zoltan Varga <[email protected]>

Backporting dotnet/runtime#59861 (mono#21532)

Fixes dotnet/runtime#72181

Co-authored-by: Ivan Povazan <[email protected]>

Backport dotnet/runtime#71436 (mono#21519)

Backport dotnet/runtime#71436
Backport of mono#21516 to 2020-02

Co-authored-by: Thays Grazia <[email protected]>

Bump nuget.exe to v6.2.1

Set app context to null on thread detach (mono#21489)

When a domain is unloaded, it is possible that an InternalThread
has a reference to an app context from the unloaded domain.

Co-authored-by: Bill Holmes <[email protected]>

[2020-02] Bump corefx to get MaxResponseHeadersLength fix (mono#21475)

Co-authored-by: Steve Pfister <[email protected]>

[mono] Remove some of the restrictions on constrained calls from gsha…

…revt methods. (mono#21471)

This is a backport of dotnet/runtime#59182.

Co-authored-by: Zoltan Varga <[email protected]>

[2020-02] Use upstream zlib 1.2.12 (mono#21460)

* Use upstream zlib 1.2.12

* [zlib] Cherrypick upstream crc32 fix

Cherrypick crc32 fix to restore pre-1.2.12 behavior

madler/zlib@ec3df00

> The previous releases of zlib were not sensitive to incorrect CRC
> inputs with bits set above the low 32. This commit restores that
> behavior, so that applications with such bugs will continue to
> operate as before.

Co-authored-by: Aleksey Kliger <[email protected]>