RFA: Check for corruption of cv_type chain

[Michael Snyder]

Jim Blandy wrote:

> If you're testing the Dwarf 2 support, you have to ignore all sorts of
> failures; why is this one any different?  

NNNNNOOOOOOOOooooooooooo!!!
We're supposed to be trying to _reduce_ the number of "ignore" failures.
Can't we xfail this on targets that don't support stabs or something?

BTW, Jim, that would include all 64-bit targets...