[Ada] Do not generate elaboration code for alignment aspect

[Ada] Do not generate elaboration code for alignment aspect

gcc/ada/

	* einfo.ads (Delayed Freezing and Elaboration): Adjust description.
	* freeze.adb (Freeze_Object_Declaration): Likewise.
	* sem_ch3.adb (Delayed_Aspect_Present): Likewise.  Do not return
	true for Alignment.
	* sem_ch13.adb (Analyze_Aspect_Specifications): Do not always delay
	for Alignment.  Moreover, for Alignment and various Size aspects,
	do not delay if the expression is an attribute whose prefix is the
	Standard package.