* sem_ch5.adb (Analyze_Loop_Statement): Element iterators
over multidimensional arrays create additional loops during
expansion. For such loops we create a label as a scope
name. Attach this label properly to tree, for use in GNATProve
over such element iterators.
* sem_attr.adb (Analyze_Attribute, case Loop_Entry): The loop to
which the attribute applies comes from source, not from expansion
of an element iterator or a quantified expression.
* exp_attr.adb (Expand_N_Attribute_Reference): Ditto.