Sat 26 Jun 2021 : moved ts_ctimer.adb to the folder Basic_Timer,
  updated system.gpr.  Modified system.gpr, as C timer is only for Windows.
  Improved system.gpr to cover tests in the subfolders.

Thu 10 Jun 2021 : defined system.gpr to build the test procedures.

Sun 23 Aug 2020 : extended communications_with_user with end of input message.

Fri 10 Jul 2020 : minor layout adjustments in communications_with_user.adb.

Sun 22 Mar 2020 : adjusted the menu to prompt for the precision in
  communications_with_user.adb.

Tue 7 Jan 2020 : extracted the instantation of duration_io from 
  time_stamps.adb to a separate file duration_io.ads.

Tue 31 Dec 2019 : modified time_stamps.adb for compiler warning.

Sun 2 Jun 2019 : in machines.adb, replaced pragma interface by pragma import.

Tue 5 Mar 2019 : commented out the obsolescent feature Interface and
  replace it with Import in system_call.adb, following a compiler warning.

Tue 20 Mar 2018 : fixed formatting error in time_stamps.adb and fixed the
  grammatical singular before the time units.  In time_stamps.adb,
  inserted "wall clock" between the "elapsed" and "time" for clarity.

Mon 19 Mar 2018 : updated time_stamps so the elapsed time also writes the
  milliseconds and properly truncates.  Changed ts_stamps.adb, ts_clock.adb.

Tue 17 Nov 2015 : moved the prompt_for_precision function from the
  extrinsic_diagonal_solvers.adb into communications_with_user.

Mon 5 Jan 2015 : added function to count occurrences of delimiter in string
  to the package string_splitters.

Sun 23 Nov 2014 : added a split function to string_splitters.

Sun 29 May 2011 : communications_with_user.adb did not refer to 
  unchecked_deallocation, removed this from the header for warning.

Fri 20 May 2011 : ts_striscan.adb did not use communications_with_user,
  as warned by compiler.  Also modified ts_strsplit.adb for warnings.

Fri 24 Sep 2010 : splitted reading a string off from communications_with_user
  into new package string_splitters, tested by ts_strsplit.adb
  Also ts_striscan.adb and ts_filescan.adb needed updating.

Sun 31 May 2009 : added package long_integer_io.adb.

Sun 4 May 2008 : one function scan in the package string_parsing for
  parsing strings for solutions, tested by ts_striscan.adb.

Sat 22 Mar 2008 : minor modification in ts_threads.adb.

Thu 10 Jan 2008 : added package multithreading to encapsulate
  the GNAT.threads package.

Wed 9 Jan 2008 : ts_threads.adb tests the GNAT interface to threads.

Thu 3 Jan 2008 : because of warnings of GNAT GPL 2006, modified
  bye_bye_message.adb and ts_time.adb.

Wed 2 Jan 2008 : because of warnings with GNAT GPL 2006, modified
  communications_with_user.adb, machines.adb and time_stamps.adb.

Thu 20 Mar 2006 : extended the package File_Scanning with the operation
  Scan_Line_for_Number, moved from standard_complex_poly_systems_io.

Mon 20 Dec 2004 : added also name to Read_Name_and_Open_file and
  Open_Input_File in communications_with_user.

Sun 19 Dec 2004 : added "name" as extra to Create_Output_File in the
  communications_with_user package.

Sun 15 Aug 2004 : created new directories Basic_Timer and Unix_Timer to
  avoid the copying of files to install windows or unix verison of phc.
  Older files were moved into Archive, which should be obsolete...

Mon 19 Jul 2004 : added new version of Read_Name_and_Create_File which
  returns the name of the file which was created.

Fri 22 Mar 2002 : new Read_Name_and_Append_File in Communications_with_User,
  appended to ts_commuser.adb to test the new facility

Fri 15 Sep 2000 : introduced "Write_Elapsed_Time" in Time_Stamps to fix
  negative seconds when the calculations ran overnight.

Fri 1 Dec 2000 : created ts_ctimer.adb to get a timer that only depends
  on ANSI C, no longer on UNIX

Tue 19 Dec 2000 : created win_timing_package and ts_wintimer.adb to
  test the timer with the C interface.

