mrb_mod_alias to use mrb_get_args("nn")
mrb_bob_missing to use mrb_get_args("n")
put pointer tables before bitmap to avoid alignment issues; ref #1353
Replace 0 with '\0' as nul terminated string.
Merge pull request #1360 from suzukaze/refactor-string.c

Replace 0 with '\0' as nul terminated string.