Fix compiler warnings:

	Fix compiler warnings:
	* libmisc/audit_help.c: Include prototypes.h to get the prototype
	of audit_help_open.
	* libmisc/salt.c: Use booleans instead of negating integers.
	* src/passwd.c: Declare the check_selinux_access prototype and
	avoid name clashes (change_user -> changed_user; change_uid ->
	changed_uid; access -> requested_access)