mplay32: add entries for found mci devices in the "Device" menu

The patch adds entries for found mci devices under the "Device" submenu. If the the user
invokes one of this menu points, the initial filter selection in the open dialog is set to the
filter for the specified device and that device is used to open the choosen file instead of
the one associated with the file's extension. If the device reports that it doesn't use files,
the open dialog is omitted and the program tries to open the device without a file
(like for the cd-audio device for example).