lualoader: allow brands to specify a shift

Some brands will want to specify a shift to make sure they're properly
centered; let it happen.

stand/lua/drawer.lua

@@ -308,6 +308,11 @@ local function drawbrand()
 
 	x = x + shift.x
 	y = y + shift.y
+	if branddef.shift ~= nil then
+		x = x +	branddef.shift.x
+		y = y + branddef.shift.y
+	end
+
 	if core.isFramebufferConsole() and
 	    loader.term_putimage ~= nil and
 	    branddef.image ~= nil then