New implementation of the conversion test, using normalization by evaluation to
native OCaml code.

Warning: the "retroknowledge" mechanism has not been ported to the native
compiler, because integers and persistent arrays will ultimately be defined as
primitive constructions. Until then, computation on numbers may be faster using
the VM, since it takes advantage of machine integers.



git-svn-id: svn+ssh://scm.gforge.inria.fr/svn/coq/trunk@16136 85f007b7-540e-0410-9357-904b9bb8a0f7