ada: Fix bug in resolution of Ghost_Predicate

ada: Fix bug in resolution of Ghost_Predicate

This patch fixes a failure of name resolution when
a range attribute reference appears in a Ghost_Predicate
and the ghost policy is Ignore.

gcc/ada/

	* sem_ch13.adb (Add_Predicate): Remove the premature "return;".
	Ghost code needs to be processed by later code in this procedure
	even when ignored; otherwise the second pass of name resolution
	fails much later. However, protect Set_SCO_Pragma_Enabled and
	Add_Condition with "if not Is_Ignored_Ghost_Pragma"; these parts
	should not happen if the ghost code is Ignored.
	* libgnat/interfac__2020.ads (Unsigned_8): Minor reformatting.
	* libgnat/interfac.ads (IEEE_Extended_Float): Minor comment
	improvement.