[06/10] msvcirt: Implement strstreambuf::setbuf

[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=16671

Your paranoid android.


=== w2000pro (32 bit msvcirt) ===
msvcirt.c:1521: Test failed: wrong buffer end, expected 0022FC70 + 0x7fffffff got FFFFFFFF
msvcirt.c:1527: Test failed: wrong put end, expected 0022FC70 + 0x7fffffff got FFFFFFFF

=== wxppro (32 bit msvcirt) ===
msvcirt.c:1521: Test failed: wrong buffer end, expected 0022FC70 + 0x7fffffff got FFFFFFFF
msvcirt.c:1527: Test failed: wrong put end, expected 0022FC70 + 0x7fffffff got FFFFFFFF

=== w2003std (32 bit msvcirt) ===
msvcirt.c:1521: Test failed: wrong buffer end, expected 0022FC70 + 0x7fffffff got FFFFFFFF
msvcirt.c:1527: Test failed: wrong put end, expected 0022FC70 + 0x7fffffff got FFFFFFFF