This is part #1 of the patches to fix 81592/82123.  The changes aren't
particularly large or invasive, but I already had them broken down
internally into distinct chunks, so I'm going to send them out that way.

This patch allows the EVRP range analyzer to be safely called even when
not optimizing.  It does no analysis in that case.   This prevents
problems if we were to ask for sprintf warnings but not have the
optimizer enabled.

Bootstrapped and regression tested on x86_64-linux-gnu.

Jeff