Merge pull request #134 from k-takata/fix-segv-in-error-str

Fix SEGV in onig_error_code_to_str() (Fix #132)
add_code_range(BBuf** pbuf, ScanEnv* env, OnigCodePoint from, OnigCodePoint to)
{
  return add_code_range0(pbuf, env, from, to, 1);
}

add_code_range(BBuf** pbuf, ScanEnv* env, OnigCodePoint from, OnigCodePoint to)
{
  return add_code_range0(pbuf, env, from, to, 1);
}
