[RFC][BZ #16549] Add sanity check for condvar alignment.

[Rich Felker]

On Sun, Feb 16, 2014 at 12:55:22PM +0100, Ondřej Bílka wrote:
> That is most of time not problem as a function will either work or
> crash.

This is not entirely true. On archs where the low bits are ignored in
pointers, passing a misaligned address will result in misinterpreting
(if reading) and corrupting (if writing) adjacent data.