[Ada] T'Image calls T'Put_Image

[Ada] T'Image calls T'Put_Image

2020-06-15  Bob Duff  <duff@adacore.com>

gcc/ada/

	* exp_put_image.ads, exp_put_image.adb
	(Image_Should_Call_Put_Image): New function to determine whether
	the call to Put_Image should be generated.
	(Build_Image_Call): New procedure to generate the call to
	Put_Image.
	* exp_imgv.adb (Expand_Image_Attribute): Use underlying types to
	bypass privacy (only in Ada 2020). If
	Image_Should_Call_Put_Image is True (which happens only in Ada
	2020), then call Build_Image_Call.
	* rtsfind.ads, rtsfind.adb: Add the necessary declarations in
	Ada.Strings.Text_Output.Buffers.
	* sem_attr.adb (Check_Image_Type): Enable the Ada 2020 case.
	* libgnat/a-stoufo.ads, libgnat/a-stoufo.adb: Use the less
	restrictive type that allows newline characters.