ImageData, texture building++, mouse movement++

- updated ports
- ozCore
  * use of constexpr for abs(), min(), max(), clamp(), ...
- ozFactory
  * ImageData class to hold image pixels and metadata
- ui
  * sub-pixel cursor accuracy
- client
  * mouse acceleration++, fixed for SDL 2.0.3
  * fixed dropped frames statistics
- builder
  * ozFactory used for building textures
Fixes, preloading++

- ozCore
  * obsolete memalloc() -> C11 aligned_alloc(), no -lrt => glibc 2.17+ required
  * fixed JSON value access tracking
  * JSON::operator << (const File&)
- ozFactory
  * fixed BGRA -> RGBA conversion when loading images
- client
  * more model loading moved into preload()