bootstrapping: optimize compiler during warmup phase

(cherry picked from commit 4a048d3)

Author: vtjnash

src/gf.c

@@ -477,6 +477,7 @@ void jl_foreach_reachable_mtable(void (*visit)(jl_methtable_t *mt, void *env), v
     }
     else {
         foreach_mtable_in_module(jl_main_module, visit, env, &visited);
+        foreach_mtable_in_module(jl_core_module, visit, env, &visited);
     }
     JL_GC_POP();
 }
@@ -501,7 +502,7 @@ JL_DLLEXPORT void jl_set_typeinf_func(jl_value_t *f)
     jl_typeinf_func = (jl_function_t*)f;
     jl_typeinf_world = jl_get_tls_world_age();
     ++jl_world_counter; // make type-inference the only thing in this world
-    if (0 && newfunc) {
+    if (newfunc) {
         // give type inference a chance to see all of these
         // TODO: also reinfer if max_world != ~(size_t)0
         jl_array_t *unspec = jl_alloc_vec_any(0);