[Ada] Use spans instead of locations for compiler diagnostics

[Ada] Use spans instead of locations for compiler diagnostics

gcc/ada/

	* errout.adb: (Error_Msg_Internal): Use span instead of
	location.
	(Error_Msg, Error_Msg_NEL): Add versions with span parameter.
	(Error_Msg_F, Error_Msg_FE, Error_Msg_N, Error_Msg_NE,
	Error_Msg_NW): Retrieve span from node.
	(First_Node): Use the new First_And_Last_Nodes.
	(First_And_Last_Nodes): Expand on previous First_Node. Apply to
	other nodes than expressions.
	(First_Sloc): Protect against inconsistent locations.
	(Last_Node): New function based on First_And_Last_Nodes.
	(Last_Sloc): New function similar to First_Sloc.
	(Output_Messages): Update output when -gnatdF is used. Use
	character ~ for making the span visible, similar to what is done
	in GCC and Clang.
	* errout.ads (Error_Msg, Error_Msg_NEL): Add versions with span
	parameter.
	(First_And_Last_Nodes, Last_Node, Last_Sloc): New subprograms.
	* erroutc.adb: Adapt to Sptr field being a span.
	* erroutc.ads (Error_Msg_Object): Change field Sptr from
	location to span.
	* errutil.adb: Adapt to Sptr field being a span.
	* freeze.adb: Use Errout reporting procedures for nodes to get
	spans.
	* par-ch3.adb: Likewise.
	* par-prag.adb: Likewise.
	* par-util.adb: Likewise.
	* sem_case.adb: Likewise.
	* sem_ch13.adb: Likewise.
	* sem_ch3.adb: Likewise.
	* sem_prag.adb: Likewise.
	* types.ads: (Source_Span): New type for spans.
	(To_Span): Basic constructors for spans.