* mln/core/concept/proxy.hxx
	(get_proxy_impl::operator): New overload (mutable) conversion
	towards the immediate subject.
	Keep ref or ptr in conversion return type.
	* mln/core/concept/site_proxy.hh (operator site): De-activate
	the static check of its presence since "site" can be either a
	ref, a const ref, or a plain type.
	* mln/core/concept/accumulator.hh (result_): Update.
	* mln/core/dpoints_pixter.hh (get_adr): Replace by conversion.
	Add a static check about the p_ref argument type.
	* mln/core/internal/site_relative_iterator_base.hh: Likewise.
	* mln/metal/fix_return.hh: New.


git-svn-id: https://svn.lrde.epita.fr/svn/oln/branches/cleanup-2008@2406 4aad255d-cdde-0310-9447-f3009e2ae8c0