Demonstrates an issue related to comdats and IPO

One of the link orders (order-a on my machine) will have a SIGFPE while the others won't. As far as I can tell, the program is well defined, since in the original program both the places that call maybe_divide store a non-zero value to ptr[0] before calling it.

More details at http://lists.llvm.org/pipermail/llvm-dev/2016-February/095833.html.