Finalize moves-based-on-type implementation.

Changes:

- Refactor move mode computation
- Removes move mode arguments, unary move, capture clauses
  (though they still parse for backwards compatibility)
- Simplify how moves are handled in trans
- Fix a number of illegal copies that cropped up
- Workaround for bug involving def-ids in params
  (see details below)

Future work (I'll open bugs for these...):

- Improve error messages for moves that are due
  to bindings
- Add support for moving owned content like a.b.c
  to borrow check, test in trans (but I think it'll
  "just work")
- Proper fix for def-ids in params

Def ids in params:

Move captures into a map instead of recomputing.

This is a workaround for a larger bug having to do with the def-ids associated
with ty_params, which are not always properly preserved when inlining.  I am
not sure of my preferred fix for the larger bug yet.  This current fix removes
the only code in trans that I know of which relies on ty_param def-ids, but
feels fragile.

src/libsyntax/ast_util.rs

@@ -256,7 +256,7 @@ pub fn ident_to_path(s: span, +i: ident) -> @path {
 
 pub fn ident_to_pat(id: node_id, s: span, +i: ident) -> @pat {
     @ast::pat { id: id,
-                node: pat_ident(bind_by_value, ident_to_path(s, i), None),
+                node: pat_ident(bind_by_copy, ident_to_path(s, i), None),
                 span: s }
 }
 
@@ -503,11 +503,8 @@ pub fn id_visitor(vfn: fn@(node_id)) -> visit::vt<()> {
                     vfn(m.self_id);
                     for vec::each(tps) |tp| { vfn(tp.id); }
                 }
-                visit::fk_anon(_, capture_clause) |
-                visit::fk_fn_block(capture_clause) => {
-                    for vec::each(*capture_clause) |clause| {
-                        vfn(clause.id);
-                    }
+                visit::fk_anon(_) |
+                visit::fk_fn_block => {
                 }
             }