Fix dependencies between kernel options:

• When both SC_PIXEL_MODE and SC_NO_FONT_LOADING are defined, quietly drop SC_NO_FONT_LOADING, because the pixel(raster) console requires font.
• When SC_NO_FONT_LOADING is defined, force SC_ALT_MOUSE_IMAGE. Without font, the arrow-shaped mouse cursor cannot be drawn.
• Fiddle and simplify some internal macros.

MFC after: 2 weeks