ada: Cleanup of Analyze_Aspect_Specifications and related code

ada: Cleanup of Analyze_Aspect_Specifications and related code

Rename Decorate to be Decorate_Aspect_Links; seems more readable.
Change it to support N_Attribute_Definition_Clause in addition
to N_Pragma. Move most calls to it into Insert_Aitem.

Move call to Set_Has_Delayed_Rep_Aspects to be near
calls to Set_Has_Delayed_Aspects.

Make Anod and Eloc variables more local to where they are used.

Misc comment improvements, including removing some useless ones.

gcc/ada/ChangeLog:

	* sem_ch13.adb (Delay_Aspect): Remove the side effect.
	(Decorate): Rename to be Decorate_Aspect_Links.
	Generalize.
	(Insert_Aitem): Call Decorate_Aspect_Links.
	* aspects.ads: Minor comment improvement: we don't need to worry;
	we just need to do it.
	* einfo.ads: Minor comment improvement.