[Ada] Crash on anonymous access-to-class-wide with tasks

[Ada] Crash on anonymous access-to-class-wide with tasks

This patch fixes a bug in which if an object declaration is of an
anonymous access type whose designated type is a limited class-wide type
(but not an interface), and the object is initialized with an allocator,
and the designated type of the allocator contains tasks, the compiler
would crash.

2019-07-03  Bob Duff  <duff@adacore.com>

gcc/ada/

	* sem_ch3.adb (Access_Definition): The code was creating a
	master in the case where the designated type is a class-wide
	interface type. Create a master in the noninterface case as
	well. That is, create a master for all limited class-wide types.

gcc/testsuite/

	* gnat.dg/task2.adb, gnat.dg/task2_pkg.adb,
	gnat.dg/task2_pkg.ads: New testcase.

From-SVN: r272986