[Ada] Add N_Has_Bounds and N_Is_Index

gcc/ada/

	* einfo-utils.adb (Next_Index): Verify input and output are
	N_Is_Index.
	* gen_il-gen-gen_nodes.adb (N_Has_Bounds, N_Is_Index): Add.
	* gen_il-types.ads (N_Has_Bounds, N_Is_Index): Likewise.
	* sem_ch3.adb (Array_Type_Declaration): Use Next, not
	Next_Index.
	* sem_ch12.adb (Formal_Dimensions): Likewise.
	* sem_util.adb (Is_Valid_Renaming): Likewise.
6 files changed