[Ada] Implement fixed-lower-bound consistency checks for qualified_expressions

[Ada] Implement fixed-lower-bound consistency checks for qualified_expressions

gcc/ada/

	* checks.adb (Selected_Range_Checks): In the case of a
	qualified_expression where the qualifying subtype is an
	unconstrained array subtype with fixed lower bounds for some of
	its indexes, generate tests to check that those bounds are equal
	to the corresponding lower bounds of the qualified array object.