[Patch] regex_iterator and regex_token_iterator implementation

[Paolo Carlini]

Hi,

>Great. This is the fixed version.

Patch is Ok with me but before committing please give a chance to Jon and other interested parties to have a look.

Two more general comments: when you opencode more than a few lines don't hesitate to add comments too (remember that the new code must be maintained over the years and not necessarily by yourself ;) Also, at some point you should add appropriate .tcc headers for the out of line functions.

Paolo