[mountmgr.sys] add unittests for registry keys of serial ports

[Dmitry Timoshkov]

"Stefan Leichter" <Stefan.Leichter at camline.com> wrote:

>> The closest match these tests belong to is dlls/kernel32/tests/comm.c
> 
> I asked where to put the implementation before i started codeing see 
> http://www.winehq.org/pipermail/wine-devel/2009-April/074476.html

That's for implementation, the tests belong to the place where public
API belongs to.

-- 
Dmitry.