package/pocketpy: new package

It is a portable Python 3.x interpreter, written in C11. It has no
dependencies other than the C standard library, which can be easily
integrated into your C/C++ project

Signed-off-by: Dario Binacchi <dario.binacchi@amarulasolutions.com>
Signed-off-by: Romain Naour <romain.naour@smile.fr>