Simple C++ string and vector classes

The classes are useful as training examples for a C+++ tutorial, for novices in C++, or if you have to avoid the standard C++ library with its classes std::string and std::vector class for any reason. It contains basic functionality compatible with the std:: versions, more functions can easily be added.

Class my_string is based on original work by Christian Stigen Larsen, 2007.

It may happen in real projects that the std library must be avoided: I needed it
because of link problems in an application using mixed libraries, especially one compiled with an old Intel compiler icc 7 (for Linux), and other libs compiled with newer compilers. Icc 7 uses an incompatible c++ standard library implementation.