Update for R16B03

R16B03 introduced a new feature which is part of the
erlang:system_info(allocator) feature list. All previous
features could be inspected by system_info({allocator,A}),
but sys_aligned_alloc cannot. So the way in which we figure
out the available allocators has been updated.
Merge pull request #6 from garazdawi/master

Update for R16B03