[Bug c++/57572] vector operators don't participate in overload resolution

[glisse at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57572

--- Comment #1 from Marc Glisse <glisse at gcc dot gnu.org> ---
Created attachment 30992
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=30992&action=edit
vector-only patch

I have had this lying around for a while. IIRC it seemed to work, but it
doesn't handle the mixed vector-scalar operations (and maybe it was missing
other things as well).