[Bug libstdc++/47921] pbump will overflow when input n is larger than 2G-1

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47921

--- Comment #7 from Paolo Carlini <paolo.carlini at oracle dot com> 2011-02-28 
14:11:39 UTC ---
Actually, fixing strstream too is easy, because it derives from
basic_streambuf<char>, which can be assumed to have __safe_pbump