- new split of proposals into jdt.core.manipulation changed the
  computeNumberOfFixesForCleanUp() method to be passed an ICleanUpCore
  that is wrappered to be an ICleanUp but this code looks for an
  IMultiFix which gets lost in wrapping
- change computeNumberOfFixesForClean() to use the fCleanUp field
  that is already stored and is an ICleanUp
- fix getCleanUp() to return fCleanUp
- fix AbstractAnnotationHover.createCompletionProposalsList() to
  just call proposal.getCleanUp() and don't do any wrapping