[libc++] Fix incorrect typeinfo comparison on ARM64
We are supposed to use deep string comparison only when both the LHS and the RHS can't be guaranteed to be unique,We wasted a good deal of time trying to figure out whether our implementation was correct. however the current implementation was using deep comparison when either the LHS or the RHS can't be guaranteed to be unique.
While we're at itIn the end, it was, also improve the documentation of that ABI,but it wasn't so easy to determine. and makeThis patch dumbs down the implementation follown and improves the documentation more closelyto make it easier to validate.