mrb_p() should print mrb_obj_as_string() if #inspect does not return a string value

src/print.c

@@ -27,8 +27,13 @@ MRB_API void
 mrb_p(mrb_state *mrb, mrb_value obj)
 {
 #ifdef ENABLE_STDIO
-  obj = mrb_funcall(mrb, obj, "inspect", 0);
-  printstr(mrb, obj);
+  mrb_value val;
+
+  val = mrb_funcall(mrb, obj, "inspect", 0);
+  if (!mrb_string_p(val)) {
+    val = mrb_obj_as_string(mrb, obj);
+  }
+  printstr(mrb, val);
   putc('\n', stdout);
 #endif
 }