[Ada] Move generation of range checks for entry families to expander

[Ada] Move generation of range checks for entry families to expander

gcc/ada/

	* checks.ads (Expander Routines): Update the description of the
	Do_Range_Check mechanism.
	* checks.adb (Selected_Range_Checks): Fix typo.
	* exp_ch9.adb: Add with and use clause for Checks.
	(Actual_Index_Expression): Generate a range check if requested.
	(Entry_Index_Expression): Likewise.
	* sem_attr.adb (Resolve_Attribute) <Attribute_Count>: Call
	Apply_Scalar_Range_Check instead of Apply_Range_Check.
	* sem_ch9.adb (Analyze_Accept_Statement): Likewise.
	* sem_res.adb (Resolve_Entry): Likewise, after having set the
	actual index type on the prefix of the indexed component.
	(Resolve_Indexed_Component): Remove useless conditional construct.