ada: Fix crash on 'Img as generic actual function
'Image is allowed as an actual for a generic formal function.
This patch fixes a crash when 'Img is used instead of 'Image
in that context.
Misc cleanups.
gcc/ada/
* exp_put_image.adb (Build_Image_Call): Treat 'Img the same as
'Image.
* exp_imgv.adb (Expand_Image_Attribute): If Discard_Names, expand
to 'Image instead of 'Img.
* snames.ads-tmpl, par-ch4.adb, sem_attr.adb, sem_attr.ads:
Cleanups: Rename Attribute_Class_Array to be Attribute_Set. Remove
unnecessary qualifications. DRY: Don't repeat "True".