configure.ac: add -fno-strict-aliasing
configure.ac: add -fno-strict-aliasing

Add -fno-strict-aliasing to disable invalid optimizations of pointer casts,
see also:

"The Strict Aliasing Situation is Pretty Bad"
https://blog.regehr.org/archives/1307

Signed-off-by: Tim Janik <6ec6ff229c4e1c5bbd5933ee92e6c5832ff023bb@gnu.org>

tim-janik/beast,tim-janik/beast,swesterfeld/beast,swesterfeld/beast,swesterfeld/beast,swesterfeld/beast,swesterfeld/beast,tim-janik/beast,tim-janik/beast,tim-janik/beast,tim-janik/beast,tim-janik/beast,swesterfeld/beast,swesterfeld/beast