This removes a feature of mounting physical CD-ROMs in DOSBox.
SDL 2.0 removed SDL_cdrom from supported libraries, so to bring this
code back, either the functionality will need to be reimplemented or
SDL_cdrom code modernized for SDL 2.0, and bundled with the repo (the
same way SDL_sound is already bundled).
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).
Cleanup before replacing SDL1.2 with SDL2.
OS/2 support was introduced in DOSBox in March 2006. OS/2 reached EOL
in December 2006.
As of 2019, OS/2 is being continued by proprietary 32-bit only ArcaOS,
although there is no official SDL2 support, despite pledges from SDL2
maintainers.
When active, this drive redirects new and changed files to a different location.
The files in the overlay and normal drive are merged on startup and kept up to date when the game changes something.
Files in the overlay are priotizedi, if they exists, above the normal files.
The drive will switch to an overlayed version of the file on the first write! (Not when opening the file in write-mode).
The overlay is capable of creating missing directories.
With the help of DBOVERLAY files, the drive keeps track of files that are present in the normal directory but deleted by the game.
All changes are preserved between sessions.
Current design principles/limitations/requirements:
1) All directories that can be used for saving, must exist already in the base before mounting. (they will be created by DOSBox if missing in the overlay)
2) All filenames inside the overlay directories are UPPERCASE and conform to the 8.3 standard except for the special DBOVERLAY files.
3) To keep point 1 valid at all times, support for creating/renaming/removing directories has been disabled.
Thanks for the help GOG.
Imported-from: https://svn.code.sf.net/p/dosbox/code-0/dosbox/trunk@4196
