* src/gpasswd.c: Use a bool when possible instead of int integers.

	* src/gpasswd.c: Use a bool when possible instead of int integers.
	* src/gpasswd.c: Avoid implicit conversion of pointers / integers
	/ chars to booleans.
	* src/gpasswd.c: Ignore the return value of putchar() and fflush()
	before exiting.
	* src/gpasswd.c: check_list() renamed is_valid_user_list(), and
	return a bool.
	* src/gpasswd.c: Ignore return value of setlocale(),
	bindtextdomain(), and textdomain().