[patch] regex_traits implementation

[Jonathan Wakely]

On 3 July 2013 05:15, Tim Shen wrote:
> All fixed. I use `_RegexMask` rather than `const _RegexMask&` just
> because, IMO, const reference is for something very large and doesn't
> need to be every-byte-accessed.
>
> Add _RegexMask::_S_valid_mask = 0x3 instead of using the literal everywhere.

Sorry for the delay, I missed this latest version - it looks excellent
and is fine to commit. Do you have svn write access or do you need
someone to commit it for you?