Some folks have already asked for a rough schedule for LLVM 11, so I
think it's time to send this.
My proposal is to essentially follow the same procedure as last time,
which would mean:
- 15 July 2020: Create the release branch. RC1 ships soon after.
- 31 July 2020: RC2
- 26 August 2020: Final (we'll try not to slip).
Please let me know what you think.