Tue 7 Mar 2017 : added explicit this-> to workspace_host.tpp.

Fri 24 Feb 2017 : path_track.tpp works for a work crew of size one...

Thu 23 Feb 2017 : defined the content of the work items in path_track.tpp.

Wed 22 Feb 2017 : added WorkItem struct in test_jobs.cpp; used explicitly
  the keyword private in jobqueue.h and worker.h.  Modified the makefile
  with the flags '-pthread' and '-lpthread' to compile test_jobs.cpp with.
  Made a first step in adding a work crew version of the manytrack in
  path_track.h, path_track.tpp, tested by test_path.cpp, with an updated
  makefile to compile test_path.cpp with the proper flags.

Tue 21 Feb 2017 : the class Worker in worker.h encapsulates pthreads,
  and is tested by test_worker.cpp.  Added test on work crew model
  to test_jobs.cpp.

Mon 20 Feb 2017 : new class defined in jobqueue.h, tested by test_jobs.cpp,
  and updated makefile.

Sun 19 Feb 2017 : extended lib2path.h and lib2path.cpp with functions to call
  the path trackers with all parameters for the phcpy2c extension module.

Sat 18 Feb 2017 : added get_value() method to parameters.h and parameters.cpp,
  with calls in lib2path.h and lib2path.cpp.  To lib2path.h and lib2path.cpp,
  added a function to get the default values for the path parameters.
  Removed the "extern" in front of the get_default_path_parameters in
  lib2path.h and lib2path.cpp.

Wed 15 Feb 2017 : lowered the number of Newton steps at the end
  and lowered the tolerance on the corrector update in parameter.h.

Tue 14 Feb 2017 : updated parameter.h with a new default value for the
  tolerance on the residual.  Increased the default number of steps.

Sun 12 Feb 2017 : added functions to lib2path.h and lib2path.cpp that allow
  to pass all 14 path parameters through to the trackers with AD.
  Fixed bug in the calls in lib2path.cpp for double double and quad doubles.

Sat 11 Feb 2017 : added parameters to the parameter list of path_track
  in path_track.h and path_track.tpp, so test_path can do path.tune().
  Added functions to lib2path.h and lib2path.cpp which take in tuned
  values of the path parameters.

Fri 10 Feb 2017 : move writing and tuning of the parameters from the
  test_parameter.cpp to a new parameter.cpp file, with added headers
  to the parameter.h, so writing and tuning belong to the parameter class.

Wed 8 Feb 2017 : new test program test_parameter.cpp to prepare for the
  interactive tuning of the parameters, implemented by the tune function.

Mon 6 Feb 2017 : stored the t value at the end of the paths in path_host.tpp,
  path_track.tpp, improved newton_host.tpp, and copied the final value of t
  to the solutions in the container, in the code of lib2path.cpp.

Sat 4 Feb 2017 : extended parameter.h with a constructor with default values
  of the parameters, cleaned up path_track.tpp, test_path.cpp,
  and also test_newton.cpp.  Added default values for double double and 
  quad double runs in parameter.h, used in path_track.tpp.
  The new defaults for parameters are used in lib2path.cpp.
  Improved newton_host.tpp, with a better test in test_newton.cpp.

Thu 2 Feb 2017 : to lib2path.h and lib2path.cpp, added interface functions
  to be called directly from C++.

Tue 31 Jan 2017 : added tracking of many paths to lib2path.h and lib2path.cpp.
  To lib2path.h and lib2path.cpp added Newton and the one path tracker.

Mon 30 Jan 2017 : arranged the printing in test_path.cpp so that it takes
  the working precision into account.  Added description to path_track.h.

Sun 29 Jan 2017 : reading of start system and start solutions added to
  test_path.cpp.  With code from ade_manypaths_d.cpp in Ada/PHCtoC
  defined the path_track.h and path_track.cpp, for use in test_path.cpp.
  
Sat 28 Jan 2017 : rewrote test_eval.cpp into a templated version,
  with better separation of tasks in separate functions.
  Fixed bug in test_eval.cpp, must pass PolySys objects by reference.
  Updated test_newton.cpp for templates and call by reference.
  Initial version of predictor_host.h, predictor_host.tpp, path_host,
  path_host.tpp, tested by test_path.cpp, with updated makefile.
  Joined ada_test_d, ada_test_dd, and ada_test_qd into lib2path
  to connect the lib interface to PHCpack to the Path data structures.

Fri 27 Jan 2017 : first templated version of newton_host.h, with the
  templated code in newton_host.tpp.  Added instructions to the makefile
  to compile the new test program test_newton.cpp.

Thu 26 Jan 2017 : removed the allocation for the result of the evaluation
  in test_eval.cpp.  Fixed path_data.h, path_data.tpp, parameter.h,
  varset.h, eval_host.h, eval_host.tpp, and test_eval.cpp.
  Defined a templated test program in test_eval.cpp.
  Placed guards to the delete statements in path_data.h, eval_host.h,
  and workspace_host.h.  Wrote 2 documentation strings in eval_host.h,
  to document the top level evaluation and differentiation operations.

Wed 25 Jan 2017 : made a first pass through eval_host.h and eval_host.tpp
  adding template directives wherever needed.  New test_eval.cpp to
  evaluate a polynomial system, with make instructions in the makefile.

Tue 24 Jan 2017 : added path_data, copied from Main, where it should not be,
  because needed by eval_host, and added workspace_host.
  Copied from Path_CPU the code for varset.h (added templates),
  also copied parameter.h, and the file eval_host.h (added templates).
  Renamed eval_host.cpp into eval_host.tpp.
