msvcrt/tests: Make test_dup2() static.

[testbot at testbot.winehq.org]

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
http://testbot.winehq.org/JobDetails.pl?Key=2829

Your paranoid android.


=== W98SE (32 bit file) ===
file.c:988: Test failed: smaller size block: Wrong error data ()
file.c:996: Test failed: smaller size block: Stdout file shouldn't contain data