[vulkan] Normalize the normal vectors on alias models

I was wondering why scaled-down quake-guy was dimmer than full-size
quake-guy. And the per-fragment normalization gives the illusion of
smoothness if you don't look at his legs (and even then...).

libs/video/renderer/vulkan/shader/alias.vert

@@ -34,6 +34,6 @@ main (void)
 	pos = (Model * vertex);
 	gl_Position = Projection3d * (View * pos);
 	position = pos;
-	normal = mat3 (Model) * norm;
+	normal = normalize (mat3 (Model) * norm);
 	st = uv;
 }

libs/video/renderer/vulkan/shader/alias_gbuf.frag

@@ -33,6 +33,6 @@ main (void)
 
 	frag_color = c;
 	frag_emission = e;
-	frag_normal = vec4(normal, 1);
+	frag_normal = vec4(normalize(normal), 1);
 	frag_position = position;
 }