When only interger ranges were supported, we knew all gimple COND 
statements were supported.  this is no longer true with float support, 
so gracefully do nothing when they are encountered.

You can choose to remove the "unsupported relational" range-ops if you 
so wish.  we shouldn't need those.,

Bootstrapped on 86_64-pc-linux-gnu with no regressions.  pushed.

Andrew