[Ada] Clean up Uint fields, remove unused routines

[Ada] Clean up Uint fields, remove unused routines

gcc/ada/

	* einfo-utils.ads, einfo-utils.adb, fe.h, einfo.ads,
	gen_il-fields.ads: Remove unused and no-longer-used routines.
	Move related routines together.  Rewrite incorrect
	documentation, and documentation that will be incorrect when
	e.g. Esize-related routines are fixed.  Remove unused field
	Normalized_Position_Max.
	* cstand.adb, exp_pakd.adb, freeze.adb,
	gen_il-gen-gen_entities.adb, itypes.adb, layout.adb,
	sem_ch10.adb, sem_ch12.adb, sem_ch13.adb, sem_ch3.adb,
	sem_ch7.adb, sem_ch8.adb, sem_ch9.adb, sem_prag.adb,
	sem_util.adb, ttypes.ads: Update calls to routines removed from
	or renamed in Einfo.Utils.
	* uintp.ads (Upos): Fix this subtype, which was unintentionally
	declared to include Uint_0.