Add a workaround hack for issue #913

I can't figure out what the real cause of this bug is, but I want
to be able to use blocks inside loops again.

src/comp/middle/tstate/collect_locals.rs

@@ -138,9 +138,11 @@ fn mk_fn_info(ccx: crate_ctxt, f: _fn, tp: [ty_param], f_sp: span,
         {constrs: res_map,
 
          // add 2 to account for the i_return and i_diverge constraints
+         // FIXME the 1u here is a kludge to make bug #913's impact somewhat
+         // smaller. it should be removed once the bug is really fixed
          num_constraints:
              vec::len(*cx.cs) + vec::len(f.decl.constraints) +
-                 vec::len(f.decl.inputs) + 2u,
+                 vec::len(f.decl.inputs) + 2u + 1u,
          cf: f.decl.cf,
          i_return: ninit(id, name),
          i_diverge: ninit(diverges_id, diverges_name),