[16/28] mshtml/tests: Use common wine_dbgstr_guid implementation from test.h

[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://newtestbot.winehq.org/JobDetails.pl?Key=4328

Your paranoid android.


=== wvista (32 bit htmldoc) ===
No test summary line found

=== w7pro64 (32 bit htmldoc) ===
No test summary line found