Mod_subst: misc reformulations

 * Remove the mind_of_delta and constant_of_delta functions,
   prefer instead the {mind,constant}_of_delta_kn functions.

 * Attempt to make subst_ind and subst_con0 more self-contained

git-svn-id: svn+ssh://scm.gforge.inria.fr/svn/coq/trunk@16247 85f007b7-540e-0410-9357-904b9bb8a0f7
Names: Modularize constant and mutual_inductive

git-svn-id: svn+ssh://scm.gforge.inria.fr/svn/coq/trunk@16248 85f007b7-540e-0410-9357-904b9bb8a0f7
Names: shortcuts for building {kn, constant, mind} with empty sections

git-svn-id: svn+ssh://scm.gforge.inria.fr/svn/coq/trunk@16249 85f007b7-540e-0410-9357-904b9bb8a0f7
kernel/declarations becomes a pure mli

 - constr_substituted and lazy_constr are now in a dedicated kernel/lazyconstr.ml
 - the functions that were in declarations.ml (mostly substitution utilities
   and hashcons) are now in kernel/declareops.ml

git-svn-id: svn+ssh://scm.gforge.inria.fr/svn/coq/trunk@16250 85f007b7-540e-0410-9357-904b9bb8a0f7