Tracking issue for stable inline assembly

[adamgreig]

The next stable Rust release, 1.59, will include stable asm!() and global_asm!() macros that finally permit us to define assembly directly in the crate without needing to distribute precompiled binaries.

I anticipate this will let us remove all the current code to support precompiled binaries, including the outlined-inlined-asm in cortex-m and the asm.S in cortex-m-rt, and make all our inline-asm features no-ops. Since this shouldn't be a breaking change to users, it could be released as a cortex-m 0.7 backport, or as part of the upcoming 0.8, and as a normal minor 0.7 release for cortex-m-rt.

This issue is for tracking progress/concerns/problems.