ada: Improved checking of uses of package renamings

In some cases, the RM 8.5.1(3.1) legality rule about uses of renamings of
limited views of packages was implemented incorrectly, resulting in rejecting
legal uses.

gcc/ada/ChangeLog:

	* gen_il-fields.ads: add new Renames_Limited_View field.
	* gen_il-gen-gen_entities.adb: add Renames_Limited_View flag for
	packages.
	* einfo.ads: add comment documenting Renames_Limited_View flag.
	* sem_ch8.adb (Analyze_Package_Renaming): Set new Renames_Limited_View
	flag. Test new Renames_Limited_View flag instead of calling
	Has_Limited_With. If Has_Limited_With is True, that just means
	that somebody, sometime during this compilation needed to
	reference the limited view of the package; so that function
	returns True too often to be used here.
	(Find_Expanded_Name): Test new Renames_Limited_View flag instead of
	calling Has_Limited_With.