[Ada] Elaboration order v4.0 and cycle detection

[Ada] Elaboration order v4.0 and cycle detection

This patch introduces a new cycle detection algorithm which is based on
Tarjan's "Enumeration of the Elementary Circuits of a Directed Graph"
algorithm, with several ideas borrowed from Jonson's "Finding all the
Elementary Circuits of a Directed Graph" algorithm.

No need for a test because the new algorithm improves the performance of
cycle detection only.

2019-07-10  Hristian Kirtchev  <kirtchev@adacore.com>

gcc/ada/

	* bindo.adb: Update the section on switches.
	* bindo-graphs.adb
	(Add_Cycle, Add_Vertex_And_Complement): Remove.
	(Create): The graph no longer needs a set of recorded cycles
	because the cycles are not rediscovered in permuted forms.
	(Cycle_End_Vertices): New routine.
	(Destroy): The graph no longer needs a set of recorded cycles
	because the cycles are not rediscovered in permuted forms.
	(Destroy_Library_Graph_Vertex): Move to the library level.
	(Find_All_Cycles_Through_Vertex, Find_All_Cycles_With_Edge):
	Remove.
	(Find_Cycles_From_Successor, Find_Cycles_From_Vertex,
	Find_Cycles_In_Component, Has_Elaborate_All_Edge): New routines.
	(Insert_And_Sort): Remove.
	(Is_Elaborate_Body_Edge): Use predicate
	Is_Vertex_With_Elaborate_Body.
	(Is_Recorded_Cycle): Remove.
	(Is_Vertex_With_Elaborate_Body): New routine.
	(Normalize_And_Add_Cycle): Remove.
	(Precedence): Rename to xxx_Precedence, where xxx relates to the
	input.  These versions better reflect the desired input
	precedence.
	(Record_Cycle): New routine.
	(Remove_Vertex_And_Complement, Set_Is_Recorded_Cycle): Remove.
	(Trace_xxx): Update all versions to use debug switch -d_t.
	(Trace_Component): New routine.
	(Trace_Eol): Removed.
	(Trace_Vertex): Do not output the component as this information
	is already available when the component is traced.
	(Unvisit, Visit): New routine.
	* bindo-graphs.ads: Add new instance LGV_Lists.  Remove instance
	RC_Sets.  Update the structure of type Library_Graph_Attributes
	to remove the set of recorded cycles.
	(Destroy_Library_Graph_Vertex): Move to the library level.
	* bindo-writers.adb (Write_Component_Vertices): Output
	information about the number of vertices.
	* debug.adb: Document the use of binder switch -d_t.  Update the
	use of binder switch -d_T.

From-SVN: r273330