stage1 支持label break, continue

stage1/spl_ast2ir.h

@@ -9,6 +9,7 @@ typedef MAP(spl_def_id_t, spl_ir_node_ref_t) spl_def2ir_map_t;
 typedef struct {
     usize cont_blk;
     usize brk_blk;
+    const char *label;
     spl_ir_node_ref_vec_t breaks;
 } spl_loop_ctx_t;
 typedef VEC(spl_loop_ctx_t) spl_loop_ctx_vec_t;