Scale HUD properly

[mattthw]

Currently the HUD was ported over using GL_SetCanvas(CANVAS_DEFAULT) but we should be using the new GL_SetCanvas(CANVAS_MENU_STRETCH) to that we can use some resolution like 630x400 for Orthography, then use screen width and height to scale them to screen:

glOrtho (0, 320MENU_SCALE, 200MENU_SCALE, 0, -99999, 99999);
glViewport (glx, gly, glwidth, glheight);