[Ada] Unnesting: check index expressions for uplevel references

[Ada] Unnesting: check index expressions for uplevel references

2018-05-28  Ed Schonberg  <schonberg@adacore.com>

gcc/ada/

	* exp_unst.adb (Visit_Node): For indexed components and attribute
	references, examine index expressions or associated expressions as well
	to record uplevel references.
	(Vist_Node): For function and procedure calls, if a formal is an
	unconstrained array and the actual is constrained, check whether bounds
	of actual have uplevel references.

From-SVN: r260841