Mon 16 Mar 2026 : to *vecvecs_container* added function to get the size
  of each stored vector, updated test_*_vecvecs_container.adb.

Sun 15 Mar 2026 : added verbose level to all operations in {double, dcmplx}_
  vecvecs_container, updated test_{double, dcmplx}_vecvecs_container.

Sat 14 Mar 2026 : new double_vecvecs_container, test_double_vecvecs_container,
  and ts_dvvcon for containers of arrays of vectors of floating-point vectors.
  Updated structures.gpr.  Copied to store vectors of complex vectors:
  new dcmplx_vecvecs_container, test_dcmplx_vecvecs_container, ts_cvvcon.

Fri 13 Mar 2026 : added new package test_systems_containers, with code taken
  from ts_syscon.adb; updated structures.gpr, because no C code in this folder.
  Added new package test_solutions_containers with code from ts_solcon.
  Added new package test_systems_pools with code from ts_syspool. 
