Sort of implementation of chunk sparsing

Issues:
* Chunks are flipped
* Slow/inefficient/badly coded
* Only blocktypes are 'compressed'
Performance improvements and chunk flipping fixed
Fixed some bugs

* Fixed undefined behaviour
* Fixed compression failure
Merge remote-tracking branch 'origin/master' into chunkysparsing
Speed and memory improvements

* Changed array to be continuous, so no more layer splitting
Nibbletypes are compressed

+ Added nibble compression
* Fixed an off by one
Blocklight and skylight now compressed
Attempt to fix errors
Maybe speed improvements?

* Use a single index to determine from when to begin copying data
* Use heightmap to determine first nonair block
Replaced all the .data() calls so the code compiles in VS2008
Implemented suggestions
Another small speed improvement?
Fixed indent
Use libc++ on OSX

Fixes issues with https://github.com/mc-server/MCServer/commit/f3dfc0349d7008efa50855c739d86918bdbf4a88 in XCode.

Tested on Mac (Makefile and XCode) and Linux.
Move to line 47.
Implemented comments
Needs the -stdlib linker flag too.
Merge pull request #936 from archshift/patch-1

Use libc++ on OSX
Merge pull request #863 from mc-server/chunkysparsing

Chunky sparsing