rare hang in both noham and ham versions

[bhuff36]

I've added a "test" that attempts to run a billion iterations of encryption followed by decryption:

https://gist.github.com/bhuff36/788646b453a1dc4abcf4ee03facda3c8

Every few iterations, it prints the remaining number of iterations.

After a while this is observed to "hang", meaning that the library gets "stuck" in one of the encryption or decryption calls, while consuming all available (single-threaded) CPU time.

This happens for both noham and ham versions.

I believe this is indicative of a bug in libntru.

The host platform I attempted to run libntru on is x86_64.