* fold-const.c (fold_unary_loc): Fold VEC_UNPACK_LO_EXPR,
	VEC_UNPACK_HI_EXPR, VEC_UNPACK_FLOAT_LO_EXPR and
	VEC_UNPACK_FLOAT_HI_EXPR with VECTOR_CST argument.
	(fold_binary_loc): Fold VEC_PACK_TRUNC_EXPR,
	VEC_PACK_FIX_TRUNC_EXPR, VEC_WIDEN_MULT_LO_EXPR
	and VEC_WIDEN_MULT_HI_EXPR with VECTOR_CST arguments.

	* gcc.dg/vect/vect-122.c: New test.

From-SVN: r181972