Exceptions caught by value incur needless cost in C++, most of them can
be caught by const-reference, especially as nearly none are actually
used. This could allow compiler generate a slightly more efficient code.

- drop unnecessary matrix initialization

* js: update build script

- support emscipten 1.38.12 (wasm is ON by default)
- verbose build messages

* js: use builtin Math functions

* js: disable tracing code completelly

  * remove race condition
  * upload _prevPts to OpenCL device explicitly before calling "sparse"

* Make cocoa windows draw faster

* Use a CALayer for rendering when possible Uses GPU to scale images, which is important because retina macs will want window sizes much larger (in pixels) than the image

* Fix mouse logic for cocoa windows

* Only halve resolution on retina if image is larger than display

- always pass DEPTH_dst value to core/arithm kernel