[Patch] Speed up parsing of ints and floats (in the "C" locale)

[Benjamin Kosnik]

> +      template<typename _CharT2>
> +        typename __enable_if<int, __is_char<_CharT2>::__value>::__type
> +        _M_find(const _CharT2*, size_t __len, _CharT2 __c) const

very nice!

-benjamin