Saner approach to lvalues and callable values in trans

LValues no longer carry information about generics and objs, instead
there's an extended form of lvalue, lval_maybe_callee, only used by
call and bind, which holds this info.

This makes it possible to take the value of a method and get a working
closure, and will (with some more work) allow us to call statically
known functions without loading from their pair.

Closes #435
Closes #758

src/comp/middle/trans_vec.rs

@@ -117,7 +117,7 @@ fn trans_vec(bcx: @block_ctxt, args: [@ast::expr], id: ast::node_id) ->
     let i = 0u;
     for e in args {
         let lv = trans_lval(bcx, e);
-        bcx = lv.res.bcx;
+        bcx = lv.bcx;
         let lleltptr =
             if ty::type_has_dynamic_size(bcx_tcx(bcx), unit_ty) {
                 InBoundsGEP(bcx, dataptr, [Mul(bcx, C_uint(i), llunitsz)])

src/test/run-pass/standalone-method.rs

 // Test case for issue #435.
-obj foo() {
-    fn add5(n: int) -> int { ret n + 5; }
+obj foo(x: int) {
+    fn add5(n: int) -> int { ret n + x; }
 }
 
 fn add5(n: int) -> int { ret n + 5; }
@@ -10,7 +10,7 @@ fn main() {
     assert (add5(7) == 12);
     assert (fiveplusseven() == 12);
 
-    let my_foo = foo();
+    let my_foo = foo(5);
     let fiveplusseven_too = bind my_foo.add5(7);
     assert (my_foo.add5(7) == 12);
     assert (fiveplusseven_too() == 12);