when evaluating a COND_EXPR, we need to evaluate both operands. With the 
recent changes to floating point, we missed that we are accidentally 
using the LHS range type for the operands.. that was fine when 
everything was an irange... but no so any more.

This patch simply uses the right range type for the temporary ranges.

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

Andrew