[Patch] Internal functions for testsuite in regex

[Paolo Carlini]

.. a final one: if you don't like all those *_debug functions around, 
both in rehex.h and regex.tcc, you could move all of them to a new 
header matching the new naming scheme, like regex_debug.h. For the time 
being I would recommend putting it in bits/, installing it, including it 
from <regex>, exactly like all the other regex bits.

A completely different option, which I also like a lot in fact, would be 
putting the new *_testsuite functions inside the already existing 
testsuite/util/testsuite/regex.h. There you would use namespace 
__gnu_test, would not require strict uglification, etc.

Paolo.