No change in behavior, so no test.

2019-08-12  Bob Duff  <duff@adacore.com>

gcc/ada/

	* libgnat/a-except.ads: Update obsolete comment, still making
	clear that this is a variant.  Add explicit default for Id
	component of Exception_Occurrence, because that value is used.
	Define Null_Occurrence less redundantly.
	* libgnat/a-einuoc.adb: Minor simplification of code.

From-SVN: r274296