Initialize absvector elements to shen.fail!

Shen 9.0 changes the namespace separator from - to . so shen-fail!
needs to be updated to shen.fail!.

NOTE: The overriding of Shen's vector function to take advantage of this
optimization is not currently working, so the Shen 9.0 import is still
working despite this missed change.
Start work on 0.5.0