explicitly disable face culling before drawing lines

Normally, this shouldn't matter, and on almost all
OpenGL drivers out there, it really doesn't, but
the Raspberry Pi 4's "V3D" Mesa driver behaves
differently: It simply won't draw any lines as long
as GL_CULL_FACE is enabled, so we need to disable
it.

similar/arch/ogl/ogl.cpp

@@ -554,6 +554,7 @@ void g3_draw_line(grs_canvas &canvas, const g3s_point &p0, const g3s_point &p1,
   
 	ogl_client_states<int, GL_VERTEX_ARRAY, GL_COLOR_ARRAY> cs;
 	OGL_DISABLE(TEXTURE_2D);
+	glDisable(GL_CULL_FACE);
 	color_r = PAL2Tr(c);
 	color_g = PAL2Tg(c);
 	color_b = PAL2Tb(c);