ada: Emit SCOs for nested decisions in quantified expressions

The tree traversal for decision SCO emission did not recurse in the
iterator specification or loop parameter specification of quantified
expressions, resulting in missing coverage obligations for nested
decisions. This change fixes this by traversing all the attributes
of quantified expressions nodes.

gcc/ada/

	* par_sco.adb (Process_Decisions): Traverse all attributes of
	quantified expressions nodes.