Add two "cat" tests

The DES code uses a number of CAT operations.  This tests two of them,
but it's n ot a particularly involved test...
Port to the lastest libflo

This requires the RSHD opcode.
Support wide input nodes

It turns out I was doing this all wrong: when I bitwise split the
input nodes I ended up with no node with the name that ended up
getting poked.  Unfortunately the Chisel test code just silently
ignores these missing nodes, which is probably why I didn't notice it
before.

I added a simple test that checks to make sure wide inputs actually
work.  Unfortunately the DES code still doesn't work correctly...