add X11 include directory in a more correctly portable way
add X11 include directory in a more correctly portable way

scrawl/mygui,scrawl/mygui,scrawl/mygui,al2950/mygui,scrawl/mygui,al2950/mygui,Anomalous-Software/mygui,fmwviormv/mygui,al2950/mygui,fmwviormv/mygui,fmwviormv/mygui,al2950/mygui,Anomalous-Software/mygui,Anomalous-Software/mygui,fmwviormv/mygui,Anomalous-Software/mygui