[C++-sig] stl_input_iterator and std::distance fix

[troy d. straszheim]

I'm going through some bugs, I can't seem to find the thread where this 
bug report originated:

   https://svn.boost.org/trac/boost/ticket/3450

The fix is on my python branch:

http://gitorious.org/~straszheim/boost/straszheim/commit/a8979df969fd44bfaa649599293ccb173f6c29c7

I haven't closed the bug as the code isn't in SVN yet.

-t