[mythtv] Ticket #4270: MythTV on Windows (with MinGW)

[Andrei Tanas]

I have one more critical QT patch - I was trying to get backend working
(successfully, the next step will be to implement a DirectShow-based
recorder), when I realized that I hit another QT bug. Since QMutex is used
all over the place, fixing this bug seems to have made the frontend more
stable too (!).

Since it's not related to MythTV itself, I don't think I should post it to
trac, but I think it's important to post it somewhere.

I will update the wiki and post a URL for download it.

Sorry guys, looks like you'll have to rebuild QT again (full recompile is
not necessary, but linking takes hours, somebody needs to fix that MinGW
linker...).