Design on adding a new API to create labels in macros

[Xudong Yang]

Hi all,

I wrote a small design to add a new API to allow macro authors to convert label literal strings into Label objects: https://docs.google.com/document/d/1_kMVWRHSBVkSsw1SLWPf3e-3RNSt55ZZYlzFzJkkwMo/edit#

Please take a look if this interests you.

Thanks,

Xudong