Added: LDM Notes for Oct. 23rd and Oct 28th, 2019

[agocke]

https://github.com/dotnet/csharplang/blob/master/meetings/2019/LDM-2019-10-23.md

1. New primitive types (nint and nuint)

https://github.com/dotnet/csharplang/blob/master/meetings/2019/LDM-2019-10-28.md

1. Discard parameters in lambdas and other methods
2. Enhancing the common type algorithm

[tannergooding]

I think the one thing missing from nint/nuint is the discussion LDM had around shifts and masking. That is, current shifts for int/uint mask the shift count to 31 and long/ulong to 63. We can't mask with a constant for nint/nuint and would either need to do (sizeof(nint) * 8) - 1 or have the framework expose some new "well-known" member.

I picked up the work item to bring forth an API proposal on corefx.