[Ada] Nested subprograms in protected subprograms improperly handled in GNAT-LLVM

[Ada] Nested subprograms in protected subprograms improperly handled in GNAT-LLVM

2020-06-17  Gary Dismukes  <dismukes@adacore.com>

gcc/ada/

	* exp_ch9.adb (Build_Protected_Subp_Specification): Add ???
	comment about the flag Has_Nested_Subprogram not being set here.
	(Expand_N_Protected_Body): If the original body for a protected
	subprogram has the flag Has_Nested_Subprogram set, then set that
	flag on the new unprotected subprogram body that's created for
	it, and reset the Scope fields of its top level declarations,
	which have been effectively taken from the original protected
	subprogram body. Add ??? comment about unclear testing of
	Corresponding_Spec.