[Ada] Fix handling of subprograms declared in a protected body

[Ada] Fix handling of subprograms declared in a protected body

2020-06-12  Arnaud Charlet  <charlet@adacore.com>

gcc/ada/

	* exp_ch6.adb (Expand_N_Subprogram_Declaration): Do nothing for
	a subprogram declared in a protected body.
	* exp_ch9.ads, exp_ch9.adb
	(Build_Private_Protected_Declaration): Moved to sem_ch6.adb.
	(Expand_N_Protected_Body): Do nothing for a subprogram declared
	in a protected body.
	* sem_ch6.adb (Build_Internal_Protected_Declaration): Moved from
	exp_ch9.adb and renamed and fixed to ensure in particular that
	such subprograms have convention Intrinsic and have no protected
	version.
	(Analyze_Subprogram_Body_Helper): Call
	Build_Internal_Protected_Declaration.
	(Move_Pragmas): Moved up and merged with the more general
	version from Build_Private_Protected_Declaration. We only want
	to copy selected pragmas, most pragmas are not suitable for a
	copy on the spec.