[regex] add support for a BOOST_NO_CREGEX mode

[vividos]

There is a BOOST_NO_WREGEX mode in Boost.Regex that
disables support for wide character regex classes when
no support is available (either BOOST_NO_CWCHAR,
BOOST_NO_CWCTYPE or BOOST_NO_STD_WSTRING has to be
defined). A BOOST_NO_CREGEX mode would be desirable to
support platforms that define BOOST_NO_ANSI_APIS and
don't have the necessary C runtime or Win32 functions.
It would also help when one wants to test if his
application does use ansi (regex) classes.

I attached a possible patch that patches the related
files in boost/regex/, but there would be considerable
work (I guess) in libs/regex/ to omit using ansi API
functions.