[Ada] No range check on fixed point to integer conversion

[Ada] No range check on fixed point to integer conversion

gcc/ada/

	* checks.adb (Apply_Type_Conversion_Checks): Minor code clean
	up.
	* exp_ch4.adb (Discrete_Range_Check): Optimize range checks.
	Update comments.
	(Expand_N_Type_Conversion): Generate range check when rewriting
	a type conversion if needed. Add assertion.
	* exp_ch6.adb (Expand_Simple_Function_Return): Minor code clean
	up.
	* sem_res.adb (Resolve_Type_Conversion): Apply range check when
	needed.  Update comments.