[Ada] Add DWARF 5 support to System.Dwarf_Line

[Ada] Add DWARF 5 support to System.Dwarf_Line

gcc/ada/

	* libgnat/s-dwalin.ads: Adjust a few comments left and right.
	(Line_Info_Register): Comment out unused components.
	(Line_Info_Header): Add DWARF 5 support.
	(Dwarf_Context): Likewise.  Rename "prologue" into "header".
	* libgnat/s-dwalin.adb: Alphabetize "with" clauses.
	(DWARF constants): Add DWARF 5 support and reorder.
	(For_Each_Row): Adjust.
	(Initialize_Pass): Likewise.
	(Initialize_State_Machine): Likewise and fix typo.
	(Open): Add DWARF 5 support.
	(Parse_Prologue): Rename into...
	(Parse_Header): ...this and add DWARF 5 support.
	(Read_And_Execute_Isn): Rename into...
	(Read_And_Execute_Insn): ...this and adjust.
	(To_File_Name): Change parameter name and add DWARF 5 support.
	(Read_Entry_Format_Array): New procedure.
	(Skip_Form): Add DWARF 5 support and reorder.
	(Seek_Abbrev): Do not count entries and add DWARF 5 support.
	(Debug_Info_Lookup): Add DWARF 5 support.
	(Symbolic_Address.Set_Result): Likewise.
	(Symbolic_Address): Adjust.