This changes the -gnatRj output from a concatenation of entities to an
array of entities, thus making it strictly conforming JSON and easier to
be parsed by means of GNATColl or Python.

Tested on x86_64-pc-linux-gnu, committed on trunk

2019-07-09  Eric Botcazou  <ebotcazou@adacore.com>

gcc/ada/

	* repinfo.ads (JSON format): Adjust.
	* repinfo.adb (Need_Blank_Line): Rename to...
	(Need_Separator): ...this.
	(Blank_Line): Rename to...
	(Write_Separator): ...this and add JSON specific handling.
	(List_Array_Info): Adjust to above renaming.
	(List_Object_Info): Likewise.
	(List_Record_Info): Likewise.
	(List_Subprogram_Info): Likewise.
	(List_Type_Info): Likewise.
	(List_Entities): Do not set Need_Blank_Line.
	(List_Rep_Info): Set Need_Separator and add JSON specific
	handling. Output a single JSON stream in the  normal case.