Thu 10 Jun 2021 : added the exec_dir attribut to trackers.gpr.

Wed 9 Jun 2021 : defined trackers.gpr to build the test procedures.

Tue 23 Feb 2021 : updated ts_correct.adb, ts_ortocor.adb, ts_path.adb for
  the renaming of drivers_for_polynomial_continuation.

Sun 8 Nov 2020 : updated drivers_to_track_*paths.adb for the renaming of
  drivers_for_poly_continuation into main_poly_continuation.

Fri 26 Feb 2016 : extended stanadard_path_trackers with a new argument for
  the Gauss-Newton corrector, adjusted drivers_to_track_standard_paths.adb.
  Extended ts_path.adb with the call to the Gauss-Newton trackers.
  Similar changes in {dobldobl,quaddobl}_path_trackers, with similar changes
  in drivers_to_track_{dobldobl,quaddobl}_paths.adb, upgraded ts_path.adb.

Thu 25 Feb 2016 : new test procedure ts_ortocor, with a fix in the
  body of the package standard_orthogonal_correctors.adb.
  New packages {dobldobl, quaddobl}_orthogonal_correctors to correct
  solutions with QRLS/SVD in double double and quad double precision.

Wed 24 Feb 2016 : new package standard_orthogonal_correctors to apply
  Gauss-Newton with QRLS or SVD as corrector in an incfix path tracker.

Fri 8 Jan 2016 : assignment of w in {dobldobl,quaddobl}_path_trackers.adb,
  and also in standard_path_trackers.adb.

Thu 7 Jan 2016 : modifications in standard_path_trackers with the addition
  of the winding number as argument for the polyhedral end games.
  This changed drivers_to_track_standard_paths.adb and ts_path.adb.
  Did the same for dobldobl_path_trackers and quaddobl_path_trackers.

Tue 6 Oct 2015 : change in dobldobl_predictors.adb for exponentiation of
  double double with 64-bit integers.

Mon 19 Jan 2015 : uncommented print statements in varbprec_path_trackers.adb.

Mon 29 Dec 2014 : extended interface of varbprec_corrector_steps with the
  tuning parameters, called in varbprec_path_tracker, tested in ts_nxtsol.
  With the mixed-precision write of solutions to string, the get_next() in
  varbprec_path_tracker.adb works!

Sun 28 Dec 2014 : fourth part to varbprec_corrector_steps to perform
  sequence of Newton steps to obtain wanted accuracy with variable precision.

Sat 27 Dec 2014 : added third part to varbprec_corrector_steps
  to do one Newton step after parsing to the proper precision.

Fri 26 Dec 2014 : to varbprec_path_tracker.adb added estimate of loss
  of precision.

Wed 24 Dec 2014 : added initialization of standard path tracker and get_next
  to varbprec_path_tracker, tested by ts_nxtsol.adb.  New package
  varbprec_corrector_steps, for use in varbprc_path_tracker.

Tue 23 Dec 2014 : separate procedure to initialize solution data in
  {standard,dobldobl,quaddobl,multprec}_path_tracker.adb.

Mon 22 Dec 2014 : extended varbprec_path_tracker with initialization of
  natural parameter homotopy and the return of the current solution,
  tested initialization in ts_nxtsol.

Sat 13 Dec 2014 : fix in initialization of multiprecision homotopy in
  multprec_path_tracker.  Started writing of new package varbprec_path_tracker 
  to implement variable precision path tracker with next() method.

Sat 6 Dec 2014 : extended standard_path_tracker with initializer for a
  natural parameter homotopy, tested by ts_nxtsol.  Did the similar extension
  for {dobldobl,quaddobl,multprec}_path_tracker, tested by ts_nxtsol.

Thu 29 May 2014 : changed drivers_to_track_{standard, quaddobl}_paths.adb
  for compiler warnings.

Thu 27 Mar 2014 : allowing random gamma constants in the generators led
  to changes in the init of all *path_tracker.a* and ts_nxtsol.adb.

Mon 2 Dec 2013 : multprec_data_on_path.a* extended with data management
  for quadratic, cubic, and quartic predictors for use in the
  multprec_path_trackers.adb, fixing a bug in phc -p for precision > 64.

Sun 1 Dec 2013 : extended multprec_dispatch_predictors.a* with higher-order
  predictors.  New pacakge multprec_data_on_path to refactor the
  multprec_path_trackers, similar as done on Mon 23 Sep 2013.

Sat 30 Nov 2013 : updated with multprec_predictors.a* with higher-order
  predictors.

Tue 24 Sep 2013 : {standard,dobldobl,quaddobl}_path_tracker.adb are
  updated to form a basic path tracker with a generator, and updated
  also ts_nxtsol.adb as well.

Mon 23 Sep 2013 : new package standard_data_on_path, refactored from
  standard_path_trackers for use in standard_path_tracker, tested by
  ts_nxtsol, to add generator to path trackers.
  Refactored {dobldobl,quaddobl}_path_trackers extracting new packages
  {dobldobl,quaddobl}_data_on_path.

Thu 13 Jun 2013 : because of natural32 and integer32, more than half of all
  files were updated.

Thu 16 May 2013 : changes in *dobl_dispatch_predictors.a* and in
  {standard,dobldobl,quaddobl}_path_trackers.adb.

Wed 15 May 2013 : added quadratic & cubic predictors to standard_predictors,
  standard_dispatch_predictors and standard_path_trackers.adb.

Tue 14 May 2013 : new {dobldobl,quaddobl}_extrapolators, tested by
  ts_extrapol.adb.  Moved the *extra* code to the new directory ../Curves.

Mon 13 May 2013 : new test program ts_extrapol.adb to develop extrapolation
  methods and higher-order predictors.  New package standard_extrapolators.

Mon 21 Jan 2013 : creation of this directory, moving code involving tracking
  from Continuation to this new directory Trackers.
  Added callback functions to the Linear_Single* routines in the
  standard_path_trackers and drivers_to_path_trackers,
  tested the writing to screen with a callback in ts_track.adb.
  Similarly, updated {dobldobl,quaddobl}_path_trackers.a* and the
  drivers_to_track_{dobldobl,quaddobl}_paths.a*.
