#2 Small error in pioz80.h

[Ysblokje]

A small error in pioz80.h prevents this project to compile with with newer GCC (10.1.0)

pioz80.h:212: multiple definition of of `g_pioz80'

on line 212
st_PIOZ80 g_pioz80;
should be
extern st_PIOZ80 g_pioz80;

[Michal Hucik]

fixed - thanks