Add missing dependencies to mayHaveNonDefUseDependency

Two interesting ommissions:
* When reordering in either direction, reordering two calls which both
  contain inf-loops is illegal.  This one is possibly a change in behavior
  for certain callers (e.g. fixes a latent bug.)
* When moving down, control dependence must be respected by checking the
  inverse of isSafeToSpeculativeExecute.  Current callers all seem to
  handle this case - though admitted, I did not do an exhaustive audit.
  Most seem to be only interested in moving upwards within a block.  This
  is mostly a case of future proofing an API so that it implements what
  the comments says, not just what current callers need.

Noticed via inspection.  I don't have a test case.