Also minor reformatting nearby.

Tested on x86_64-pc-linux-gnu, committed on trunk

gcc/ada/

	* gen_il-gen-gen_entities.adb (Record_Field_Kind,
	Allocatable_Kind): Add new abstract kinds.
	(Constant_Or_Variable_Kind): Likewise.
	(E_Constant, E_Variable, E_Loop_Parameter): Use them.
	(E_Discriminant, E_Component): Likewise.
	* gen_il-types.ads (type Opt_Type_Enum): Add them.