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

	* src/groupmod.c: Use a bool when possible instead of int
	integers.
	* src/groupmod.c: Avoid assignments in comparisons.
	* src/groupmod.c: Add brackets and parenthesis.
	* src/groupmod.c: Avoid implicit conversion of pointers / integers
	/ chars to booleans.
	* src/groupmod.c: Use a %lu format to print GIDs, and cast the GID
	to (unsigned long int).
	* src/groupmod.c: Ignore return value of setlocale(),
	bindtextdomain(), and textdomain().
	* src/groupmod.c: Ignore the return value of pam_end() before
	exiting.