gtk: unitselect.c not using GINT_TO_POINTER
Compiling with tcc (but supposedly is a problem with other compilers too in other architectures):
src/client/gui-gtk-3.22/unitselect.c:418: error: cast between pointer and integer of different size
Compiling with tcc (but supposedly is a problem with other compilers too in other architectures):
src/client/gui-gtk-3.22/unitselect.c:418: error: cast between pointer and integer of different size