Implement support for Chill POWERSETs.

	Implement support for Chill POWERSETs.
	* ch-exp.y (operand_2):  Implement 'Element IN PowerSet'.
	* ch-typeprint.c (chill_type_print_base):  Handle POWERSETs.
	* ch-valprint.c (chill_val_print):  Handle TYPE_CODE_SET.
	* eval.c (evaluate_subexp):  Implement BINOP_IN.
	* expression.h (enum exp_opcode):  Added BINOP_IN.
	* gdbtypes.c (create_set_type), gdbtypes.h:  New function.
	* stabsread.c (read_type):  If 'S', create a set type.
	* valarith.c (value_bit_index, value_in), value.h:  New functions,
	for indexing in SETs.