[Ada] Fix Enclosing_Subprogram for protected entries and task entries

[Ada] Fix Enclosing_Subprogram for protected entries and task entries

2018-07-17  Ed Schonberg  <schonberg@adacore.com>

gcc/ada/

	* sem_util.adb (Enclosing_Subprogram): Protected entries and task
	entries must be treated separately: task entries are within the
	enclosing subprogram of the task type, while protected entries are
	transformed into the corresponding Protected_Body_Subprogram, which is
	the enclosing_subprogram of any subprogram declared within the entry
	body.

From-SVN: r262778