command_util: Write array definition in header mode.

command_util: Write array definition in header mode.

This modifies command_util.sh so that when it is called in header mode,
it also defines a macro for the array of all commands. command.c and
audiod_command.c are changed to use the new preprocessor macro.

This allows to get rid of the *command_list.c files completely. We may
hence remove these files from the various lists of errlist objects
in configure.ac. and from error.h. A subsequent patch will clean up
the parts that have become unused by this commit.