[Ada] Replace packed records with integers in low-level implementation

[Ada] Replace packed records with integers in low-level implementation

gcc/ada/

	* atree.ads (Slot): Change to modular type.
	(Slot_1_Bit): Delete.
	(Slot_2_Bit): Likewise.
	(Slot_4_Bit): Likewise.
	(Slot_8_Bit): Likewise.
	(Slot_32_Bit): Likewise.
	* atree.adb (Get_1_Bit_Val): Adjust to above change.
	(Get_2_Bit_Val): Likewise.
	(Get_4_Bit_Val): Likewise.
	(Get_8_Bit_Val): Likewise.
	(Get_32_Bit_Val): Likewise.
	(Set_1_Bit_Val): Likewise.
	(Set_2_Bit_Val): Likewise.
	(Set_4_Bit_Val): Likewise.
	(Set_8_Bit_Val): Likewise.
	(Set_32_Bit_Val): Likewise.
	(Print_Atree_Info): Likewise.
	(Zero): Likewise.
	* atree.h (Get_1_Bit_Field): Likewise.
	(Get_2_Bit_Field): Likewise.
	(Get_4_Bit_Field): Likewise.
	(Get_8_Bit_Field): Likewise.
	(Get_32_Bit_Field): Likewise.
	(Get_32_Bit_Field_With_Default): Likewise.
	* types.h (slot_1_bit): Delete.
	(slot_2_bit): Likewise.
	(slot_4_bit): Likewise.
	(slot_8_bit): Likewise.
	(slot_32_bit): Likewise.
	(any_slot): Change to unsigned int.
	(Slot_Size): New macro.