Direct3D hasn't worked for more than a year now, and there don't seem to
be any efforts to revive it. Remove it and concentrate on better OpenGL
support.
A large number of g++ versions ship a <regex> that declares all of the
required functions, but don't actually implement them, making using them
result in a linker error.
Fallback to Boost.Regex if the host C++11 <regex> implementation is
broken; the interface is the same anyway, only differing in the
containing namespace.
Unfortunately, Boost.Regex is not a header-only library, but this is not
a big deal because all major Linux distributions ship it, and Visual
Studio implements <regex> since 2010 (the oldest version we still
support).
In practice, only the xrandr code path received any testing. Since Clonk
works fine without changing the resolution, this will not terribly
inconvenience anybody still stuck on old systems without xrandr.
Also only minimize the window when the resolution was changed.
The minimization is there to prevent accidental focus restoration
resulting in unwanted resolution switching.
USE_FMOD define renamed to HAVE_FMOD to bring it in line with HAVE_SDL_MIXER.
MCI removed since nobody was using it anyway, and half of its functions were
stubs.