GNATprove changed the name of the pragma Annotate used to verify that
a subprogram always returns normally. It is now called Always_Return
instead of Terminating.

Tested on x86_64-pc-linux-gnu, committed on trunk

gcc/ada/

	* libgnat/s-aridou.adb: Use Always_Return instead of Terminating
	to annotate termination for GNATprove.
	* libgnat/s-arit32.adb: Idem.
	* libgnat/s-spcuop.ads: Idem.