If some compilers complain about using
std::string;, and if the "hack" for gtk-- mentioned above
does not work, then I see two solutions:
Define std:: as a macro if the compiler
doesn't know about std::.
#ifdef OLD_COMPILER
#define std
#endif
(thanks to Juergen Heinzl who posted this solution on
gnu.gcc.help)
Define a macro NS_STD, which is defined to
either "" or "std"
based on an autoconf-test. Then you should be able to use
NS_STD::string, which will evaluate to
::string ("string in the global namespace") on
systems that do not put string in std::.  (This is untested)
