ada: Fix inserting of validity checks in lock-free protected subprograms

ada: Fix inserting of validity checks in lock-free protected subprograms

Validity checks for statements in a lock-free implementation of
protected subprogram were wrongly inserted in front of the original
statements. This happened because the lock-free implementation was
created as a shallow copy, where only the protected body statements were
copied while its children still had the Parent pointing to the original
statements.

gcc/ada/

	* exp_ch9.adb (Build_Lock_Free_Protected_Subprogram_Body): Replace
	shallow copy of protected statements with a deep copy.