nxcomp: Set TokenSize to 1536 for link type ADSL and WAN. Improving non-xrender based  browser scrolling behaviour when link type is set to ADSL or WAN.

 In the 40-ies (talking about release version numbers), Firefox started
 using the Skia library [1] for client-side rendering of browser content.

 With current versions of Firefox you can switch between libXrender based
 rendering (esp. of Fonts) and Skia based rendering:

    gfx.xrender.enabled = true|false

 Some time around Firefox 52, the default for the gfx.xrender.enabled
 setting got changed by Firefox upstream from true to false. So nowadays,
 Firefox uses Skia by default.

 However, it turns out that Skia scales really badly on remote X11
 connections. Scrolling of long web pages becomes really jolty.

 Something similar could be observed earlier already when using
 Chrome or Chromium (which also has been using Skia for some time
 now).

 This change in nxcomp works around those issues and greatly
 improves scrolling and general browser experience on medium
 throughput networks (like cable modem, ADSL, HDSPA, slow LTE).

 [1] https://en.wikipedia.org/wiki/Skia_Graphics_Engine

 Fixes ArcticaProject/nx-libs#443.