'cam_pos_nodes -/+ box_nodes_d' can exceed the range of v3s16
when a player is near the world edge using a large view range
This previously caused world to disappear
Create new function getBlocksInViewRange() called from
updateDrawList() and renderMap()
Correct code style throughout updateDrawList() and renderMap()

* Sky: rename Box => m_box and inline getBoundingBox
* Uniformize aabbox3d<f32> to aabb3f

All places that lock this mutex are only called by the main thread:
ClientMap::updateCamera(), ClientMap::updateDrawList(), ClientMap::renderMap(), ClientMap::renderPostFx().

  * Rename everything.
    * Strip J prefix.
    * Change UpperCamelCase functions to lowerCamelCase.
  * Remove global (!) semaphore count mutex on OSX.
  * Remove semaphore count getter (unused, unsafe, depended on internal
    API functions on Windows, and used a hack on OSX).
  * Add `Atomic<type>`.
  * Make `Thread` handle thread names.
  * Add support for C++11 multi-threading.
  * Combine pthread and win32 sources.
  * Remove `ThreadStarted` (unused, unneeded).
  * Move some includes from the headers to the sources.
  * Move all of `Event` into its header (allows inlining with no new includes).
  * Make `Event` use `Semaphore` (except on Windows).
  * Move some porting functions into `Thread`.
  * Integrate logging with `Thread`.
  * Add threading test.

NOTE 1: This does not mean a 2x increase in framerate. Increase in fps may be up to 1-2fps
NOTE 2: This local 'caching' of settings is not optimal and an alternative solution will be worked on after 0.4.11 is released

Add (experimental) support for topbottom as well as sidebyside 3d mode

- Don't select blocks for drawing in every frame
- Sort meshbuffers by material before drawing

Switch the license to be LGPLv2/later, with small parts still remaining as GPLv2/later, by agreement of major contributors