Travis build for halostatue/diff-lcs fails in rbx 1.9 mode

[Austin Ziegler]

https://travis-ci.org/halostatue/diff-lcs/jobs/6241195

The corresponding jobs for other 1.9 versions work. I'm working on a simplified test case to try to identify, but it's going to take a little time.

This was found as part of the automated testing for halostatue/diff-lcs#17.