Added global sound control option in bochsrc and config interface
- added 'sound' option to select the driver and the wave output device
  (see bochsrc sample for details)
- the wave device option of sb16 and es1370 is now only used to set up the
  wave input device (if necessary)
- cleaned up the speaker code to initialize the 'sound' case correctly


git-svn-id: svn://svn.code.sf.net/p/bochs/code/trunk@11726 6c8e4198-a580-4521-a02f-c9ae86df1db9