[testsuite/alpha] Add test for step over fbne instruction

[Richard Henderson]

> Thanks for the couple of suggestions. Is the attached better?

Yes, though I'm confused as to why you didn't use the 4 or 5 insn
hand-coded routine that I gave you, which is more like what you would
get from the compiler with -O2 -ffast-math.

In particular, using your -O0 compiler generated version doesn't let
you *actually* test the edge conditions of fbge, should you wish to
do so.  E.g. passing in -0.0, NaN, +Inf, 0x0.0000000000001p-1022, etc.


r~