Rename IROps for reciprocal estimate, reciprocal step, reciprocal sqrt
estimate and reciprocal sqrt step, to be more consistent.  Remove
64FxWhatever versions of those ops since they are never used.  As a
side effect, observe that RSqrt32Fx4 and Rsqrte32Fx4 are the same and
hence fix the duplication, at the same time.  No functional change.


git-svn-id: svn://svn.valgrind.org/vex/trunk@2932 8f6e269a-dfd6-0310-a8e1-e2731360e62c