[7/8] msvcirt: Implement ostream::operator<< for streambuf

[Marvin]

Hi,

While running your changed tests on Windows, I think I found new failures.
Being a bot and all I'm not very good at pattern recognition, so I might be
wrong, but could you please double-check?
Full results can be found at
https://testbot.winehq.org/JobDetails.pl?Key=23764

Your paranoid android.


=== wxppro (32 bit msvcirt) ===
Found no trace of the test summary line or of a crash

=== w2003std (32 bit msvcirt) ===
Found no trace of the test summary line or of a crash