In August 2013, Arne added support for alignment to block_allocator.
In doing so, he also introduced a dependency on
memalign/posix_memalign.
I was planning on rewriting this support to work without memalign, but
then I started looking for places which _use_ this functionality, and
found none. Pike seems to build just fine without it. If it's dead
code, maybe it's better to just remove it?