+ creating a branch for a xpressive extension that allows nesting
of regular expressions

svn path=/branches/xpressive/nested_dynamic_regex/boost/xpressive/; revision=38759
* Addition of a compiler for nested dynamic regular expressions. 

svn path=/branches/xpressive/nested_dynamic_regex/boost/xpressive/; revision=38761
oops they should be public.. 

svn path=/branches/xpressive/nested_dynamic_regex/boost/xpressive/; revision=38763
* due to references to other regexes, this may not be copyable

svn path=/branches/xpressive/nested_dynamic_regex/boost/xpressive/; revision=38805
* adding regex_id and name lookup functions. 

svn path=/branches/xpressive/nested_dynamic_regex/boost/xpressive/; revision=39152