This patch corrects the verification of 'Address clauses to avoid
processing a clause where the prefix of the attribute is a generic
formal object.

2019-07-08  Hristian Kirtchev  <kirtchev@adacore.com>

gcc/ada/

	* sem_ch13.adb (Analyze_Attribute_Definition_Clause): Do not
	register an address clause when its prefix denotes a generic
	formal object.

gcc/testsuite/

	* gnat.dg/addr13.adb, gnat.dg/addr13.ads: New testcase.

From-SVN: r273218