integer-pack2.C: Require int32 effective target.

	* g++.dg/ext/integer-pack2.C: Require int32 effective target.
	Don't include limits.h.
	(w): Conditionalize on long long wider than int.  Use
	1LL << (__SIZEOF_INT__ * __CHAR_BIT__) instead of
	-9223372036854775808.
	(x): Use __INT_MAX__ instead of INT_MAX.

From-SVN: r248427