[doctest] run with "--help" for options

root
===============================================================================
subcases.cpp(0)
TEST CASE:  subcases can be used in a separate function as well
  from function...

subcases.cpp(0) MESSAGE!
  print me twice

===============================================================================
subcases.cpp(0)
TEST CASE:  subcases can be used in a separate function as well
  from function...
  sc1

subcases.cpp(0) MESSAGE!
  hello! from sc1

===============================================================================
subcases.cpp(0)
TEST CASE:  subcases can be used in a separate function as well

subcases.cpp(0) MESSAGE!
  lala

===============================================================================
[doctest] test cases:      3 |      3 passed |      0 failed | 
[doctest] assertions:      0 |      0 passed |      0 failed |
[doctest] Status: SUCCESS!
Program code.
