Judging by the usage, this header belongs in there instead of being
limited to dos module only. This change makes it easier to reuse code
for new features related to drives mounting/unmounting.
Also, remove all traces of these interfaces from user manual (README
file) and man page (docs/dosbox.1).
MCI (Media Control Interface) was a primary Windows interface. Code
comments and documentation claimed, that it's only for "NT, 2000, XP"
but the code was enabled for Windows 2000 or later (version > 4.0).
DX (Digital audio eXtraction (?)) could be forced on any Windows with
autodetection working only on Vista and Windows 7 (code was disabled for
Windows 8 or later - probably unintentionally).
DIO used DeviceIoControl interface and Windows-specific ioctl calls.
All 3 interfaces depend on SDL and SDL_cdrom functionality to work.
SDL_cdrom 1.2 implementation uses MCI on Windows to provide the same
functionality.
ASPI was supported by Microsoft only for Windows 95, 98 and, ME.
Adaptec supported this interface going forward for Windows NT, 2000,
and XP (32-bit only).
Name 'visualc_net' invokes old names for Visual Studio
(Visual Studio .NET 2002 or 2003), which has no relation to content of
this subdirectory.
Also, by renaming this directory we mitigate chance, that during
merge-in from svn/trunk git will automatically inject some values from
from upstream, incompatible version of solution files. By sheer
luck this might happen without causing a conflict. Never happened so
far, but there's no point in risking it.
