This patch fixes an issue whereby a complicated set of generic formal
packages in conjunction with use_clauses may cause a crash during
visibility checking due to a homonym being out of scope during the
checking stage.

2018-11-14  Justin Squirek  <squirek@adacore.com>

gcc/ada/

	* sem_ch8.adb (Use_One_Package): Add test for out-of-scope
	homonyms.

gcc/testsuite/

	* gnat.dg/generic_pkg.adb: New testcase.

From-SVN: r266126