message: Update version to 0.6
diff: /**
  - * meshoptimizer - version 0.5
  + * meshoptimizer - version 0.6
  *
  * Copyright (C) 2016-2017, by Arseny Kapoulkine (arseny.kapoulkine@gmail.com)
  * Report bugs and download new versions at https: *github.com/zeux/meshoptimizer
  #include <stddef.h>
  /* Version macro; major * 100 + minor * 10 + patch */
  -#define MESHOPTIMIZER_VERSION 50
  +#define MESHOPTIMIZER_VERSION 60
  /* If no API is defined, assume default */
  #ifndef MESHOPTIMIZER_API
  