[Ada] No_Task_Parts aspect

[Ada] No_Task_Parts aspect

gcc/ada/

	* aspects.ads (No_Task_Parts): New aspect.
	* snames.ads-tmpl: Add the aspect name.
	* exp_ch6.adb (Might_Have_Tasks): Return False if this is a
	class-wide type whose specific type has No_Task_Parts.
	* freeze.adb (Check_No_Parts_Violations): This is an adaptation
	of the procedure formerly known as
	Check_No_Controlled_Parts_Violations, which now supports both
	No_Controlled_Parts and No_Task_Parts.  It takes a parameter
	indicating which aspect is being checked.
	(Freeze_Entity): Call Check_No_Parts_Violations for both
	aspects.
	* sem_ch13.adb (Analyze_Aspect_Specifications): The code for
	Aspect_No_Controlled_Parts already works as is with
	Aspect_No_Task_Parts.
	* libgnat/a-iteint.ads: Add No_Task_Parts aspect to the two
	iterator iterfaces.
	* doc/gnat_rm/implementation_defined_aspects.rst: Add
	documentation for the No_Task_Parts aspect.
	* gnat_rm.texi: Regenerate.