Plan for renaming asm! macro to llvm_asm! #140

The change to rename the asm! macro to llvm_asm! was just approved in rust-lang/rust#68404, so I expect that it will be in tomorrow's nightly. As far as I understand it, the old asm! will continue to work for now, but deprecated soon.

To avoid breakage, I think it makes sense to make it a minor release to avoid breakage for people that pinned an older nightly. The deprecation period should then be enough time for users to switch to the new version