Misc l3fp changes.  Some unused functions deleted.

In extended multiplication, bring the continuation code
in front of the result at the end of the calculation,
rather than bringing it step by step closer to the start.
Some functions get renamed or deleted, no large change.


git-svn-id: http://www.latex-project.org/svnroot/experimental/trunk@4617 de43f980-851b-0410-b2f7-c40aca1f87e0