Converted AT NVR to be a device, so it gets auto-closed.
Added new machine_close() function which calls optional machine-custom close, updated machine table.
Small fixes here and there.
Re-wored the CDROM code to have a 'speeds' table instead of ugly hard-coding.
This needs some more work to cleanly get rid of all warnings.
Track/sector and CHS calculation should use sensible bit widths, for
example. Some other functions can also be combined into one.
Moved the SIO files to a new sio/ folder.
Added the 'version.h'stuff, added Makefile rule to generate the Manifest file for Windows.
Re-worked the About dialog - it now includes more info.
Several cleanups and fixes here and there.
Updated (Windows) UI to properly handle resets and changes in Settings.
Updated to no longer scan for roms at startup.
