audiod: Move UID check from audiod_command.c to audiod.c.

audiod: Move UID check from audiod_command.c to audiod.c.

check_perms() is the only reason for the gengetopt config pointer
being public and for passing the whitelist pointer to handle_connect()
in audiod_command.c. The code get less convoluted by moving the
permission check to audiod.c where both the conf pointer and the
uid_whitelist are defined.

This introduces the new public function uid_is_whitelisted() in
audiod.c which replaces check_perms(). This allows to

	* pass only the UID to the check function,
	* drop the whitelist pointer argument from handle_connect(),
	* make the conf pointer in audiod.c static.

The patch also reorders the function declarations in audiod.h a bit
to separate the functions defined in audiod.c from those defined
in audiod_command.c.