[Ada] Fix scopes for local variables in task/protected bodies

[Ada] Fix scopes for local variables in task/protected bodies

No impact on compilation with GCC.

2019-07-09  Ed Schonberg  <schonberg@adacore.com>

gcc/ada/

	* sem_util.adb (Scope_Within_Or_Same): Handle properly task
	bodies and protected bodies, so that local variables within have
	their proper scopes after these constructs have been rewritten
	during expansion. This patch resembles but is not identical to
	the code in Scope_Within.

From-SVN: r273269