@brson and I were talking with some LLVM guys today, and allocators an alignment came up. It's a little unclear why we need to force this alignment on all allocations in the standard library by default. 

The only current use case of this that I know of is SIMD. Otherwise, almost all other software in existence manages to get by with just `malloc()`. Additionally, it's not that SIMD doesn't work, it's just slower with unaligned accesses, and it's only relevant for the much newer SIMD instructions (from my understanding).

What I'm a little worried about is that all of a sudden Rust is incompatible with the system allocator as a result of this change. We make up for it by bundling an allocator, but that's appearing to be unacceptable for some distributions (perhaps). It seems like it would be nice to have an "aligned allocator" built for use cases such as SIMD, which doesn't seem like it'll be the common use case.

This all plays into the overall allocator design, however, so this may be an ok route to take for now. This is currently an internal detail which we're at liberty to change at will (due to being in `std::rt`), just wanted to write down my thoughts.