Make builtin binding fast again by binding only referenced symbols

Avoid doing the internal binding of top-level symbols in the parser,
leaving that work to be done in a post-processing step. For builtins,
this lets us do a reference-aware bind step (block_bind_incremental)
*after* generating builtins/0.

Libraries are a bit trickier since they may be bound multiple times, so
instead of thinking through the implications I added (block_bind_self)
to resolve all internal symbols immediately.

src/parser.c

@@ -2423,7 +2423,7 @@ yyreduce:
   case 9:
 #line 333 "src/parser.y" /* yacc.c:1646  */
     {
-  (yyval.blk) = block_bind((yyvsp[-1].blk), (yyvsp[0].blk), OP_IS_CALL_PSEUDO);
+  (yyval.blk) = block_join((yyvsp[-1].blk), (yyvsp[0].blk));
 }
 #line 2429 "src/parser.c" /* yacc.c:1646  */
     break;