[Ada] Crash on dispatching conditional entry call

[Ada] Crash on dispatching conditional entry call

2020-06-11  Javier Miranda  <miranda@adacore.com>

gcc/ada/

	* exp_ch9.adb (Expand_N_Conditional_Entry_Call): Replace call to
	New_Copy_List by calls to the new routine
	New_Copy_Separate_List.
	* sem_util.ads (New_Copy_Separate_List, New_Copy_Separate_Tree):
	New routines.

	* sem_util.adb (New_Copy_Separate_List, New_Copy_Separate_Tree):
	New routines.
	(New_Copy_Tree): Extend the machinery that detects syntactic
	nodes to handle lists of indentifiers with field More_Ids;
	otherwise such nodes are erroneously handled as semantic nodes.
	Copy aspect specifications attached to nodes.
	* sem_ch12.adb (Copy_Generic_Node): Protect reading attribute
	Etype.