Add extra includes for X_ShmAttach
Remove unused variables
'static' keyword goes first
Constify pointers to static strings
Don't attempt to create the sound device

If /dev/dsp is missing, don't create it.  Otherwise you end up with a
file containing all the audio produced during execution.

Now it is possible that someone wants to capture the audio to a file,
but the code performs ioctl() on the file descriptor which makes no
sense for a regular file.  We won't cater to that use case.
Remove the unused mode argument to open() calls without O_CREAT
Remove the manual umask operations in calls to open()
Replace system("/bin/mkdir") with mkdir()
Remove generated files
Modernize the autotools

This drops some obsolete macros and also drops the getopt check.  For
the latter, we should probably be using gnulib.
Move sources to a subdirectory
Remove old RCS keywords
Don't depend on having table.x86 in the same directory

This fixes `make distcheck` which does a VPATH build.
Mark the stack as non-executable