GL and AL classes, Vorbis sounds support

- more '@'-path related fixes
- ozEngine
  * doc++
  * GL class, wraps glCheckError() -> GL::checkError(), glInit() -> GL::init()
  * AL class wraps alCheckError() -> AL::checkError()
    + buffferDataFromFile()
    + Streamer sub-class
    + stream rewinding
  * ALBuffer, ALStreamingBuffer ported to AL class
- client
  * Ogg Vorbis event sounds supported
- cmake
  * doc target removed