[Patch] match_results::format and regex_replace

[Paolo Carlini]

Great indeed!

More comments later. First nit: please review the various regex_replace 
overloads vs inline: if I'm not misreading the diff I see large ones 
inline and small ones out of line!?! Should we have a regex.tcc?

Also, old story about ChangeLogs ;) This is not ok:

     	* include/bits/regex.h: Implement match_results::format and
     	regex_replace.


use something like:

     	* include/bits/regex.h (match_results::format, regex_replace):
	Implement.

That is, function names *always* between round brackets.

Paolo.