[Ada] Crash in tagged type constructor with task components

[Ada] Crash in tagged type constructor with task components

2020-06-17  Javier Miranda  <miranda@adacore.com>

gcc/ada/

	* exp_ch6.adb (Has_BIP_Extra_Formal): New subprogram.
	(Needs_BIP_Task_Actuals): Add support for the subprogram type
	internally generated for dispatching calls.
	* exp_disp.adb (Expand_Dispatching_Call): Adding code to
	explicitly duplicate the extra formals of the target subprogram.
	* freeze.adb (Check_Extra_Formals): New subprogram.
	(Freeze_Subprogram): Fix decoration of Extra_Formals.
	* sem_ch3.adb (Derive_Subprogram): Fix decoration of
	Extra_Formals.