Update icu support code to use the new checking-constructors.
Update tests to check the full Unicode character range (as of Unicode V6).
Add minimal docs describing the iterators.
[SVN r73271]
2) Changed std::copy calls on VC8 to avoid "dangerous code" warnings.
3) Moved backreference and octal escape code into line with POSIX-extended requirements.
4) Changed match_results leftmost-longest rules to stop unnecessary std::distance computations (an optimisation for non-random access iterators).
5) Changed C lib calls to use "safe" versions of string API's where available.
6) Added many new POSIX-extended leftmost-longest tests, to verify the above.
[SVN r27880]
