This patch provides a basic oracle which doesn't do anything, but will 
still respond when queried.  This allows passes to avoid the NULL check 
for an oracle pointer before they do anything, and results in a slight 
speedup in VRP, and a slightly more significant 0.3% speedup in jump 
threading..

It also unifies the register and query names to nor specify what is 
already apparent in the parameters.

Bootstrapped on x86_64-pc-linux-gnu with no regressions.  Pushed.