const-vec-of-fns.rs hits a codegen bug on OS X x86_64

[thestinger]

I don't have access to OS X so I have no way to figure this one out. I'm just going to xfail the test.

It appears to be something like SIGILL or a segmentation fault but the test runner doesn't report the specific cause of the failure.

[metajack]

Visiting for triage. Nothing to add.

[flaper87]

Visiting for triage. Nothing to add