[v3 patch] <regex> refactoring - pull out common data members as _Context

[Tim Shen]

Hi,

As the changes grow
(https://github.com/innocentim/gcc/commits/master), it's getting
harder to rebase them onto svn trunk. Can we start slowly reviewing
and checking these in? Should I post them one by one to the lis?

These patches typically break one giant piece of code (mainly
_Executor::_M_dfs) into different smaller ones and fix mostly known
issues and standard conformance issues.


-- 
Regards,
Tim Shen