3.15.4
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* Overhaul the programming guidelines (Philip Withnall)
* Restructuring of the C platform demos (Bastian Ilsø)
* Improvements to the platform overview (Bastian Ilsø, Philip Withnall)
* Updated translations:
  el      (Dimitris Spingos)
  es      (Daniel Mustieles, Adrian Perez Dominguez)