Some pretty brute-force compiler warning fixes

warning:
  narrowing conversion of ‘rect.FIFE::RectType<int>::w’ from
  ‘const int’ to ‘Uint16 {aka short unsigned int}’ inside { } is
  ill-formed in C++11 [-Wnarrowing]

Closes #789
 * Updated Glee from 5.4 to 5.5 and added hack for Mac OS 10.9 build issue. refs #825
 * Enhanced OpenGL backend. refs #822
Depth buffer was added and for that two new options. So a client can enable or disable depth buffer rendering with GLUseDepthBuffer. Additionally the value for the alpha test can be changed with GLAlphaTestValue. Note that SortingStrategy is ignored and some special light things may not work with depth buffer.
The OpenGLe backend is still available. If no one has objections, it may be removed.
Furthermore the static layer function was changed so that it should be possible to mix static with nonstatic layers. And it works without FBO, too. fixes #765
Merge pull request #824 from fifengine/t789

Some pretty brute-force compiler warning fixes
 * More work on OpenGL backend. refs #822
Merge branch 'master' of https://github.com/fifengine/fifengine
 * Removed VertexPointer and AlphaTest hacks. refs #822
 * Reduced overlay code size and added partial sorting. refs #822
Made FIFE compatible with CEGUI-0 while retaining compatibility with 0.7.9 and lower. To enable it pass -enable-cegui-0 to scons. Note that it is not possible to build for both cegui versions, cegui-0 will always override cegui.
Refs #832
Increase version to 0.4.0 for upcoming release.
 * Overlays now also use the alpha value of the client. refs #822
When using scons, if the fifechan module is build the files for it will now be also installed to python.
Fixed compiler warnings and an multicell pathfinder bug.
Fix MacOS build.

Adds a build script for mac that can be used to run build on travis.ci.
Change travis build script to run Linux build by default again.

Comments on how to run the mac build are included
Added to fife_tests an Heightmap Test and the corresponding Tileset.
The name of a required library will now not be convered to lowercase when calling pkg-config or trying finding a configure command for the library. This fixes finding libraries on case-sensitive system using these methods.
Removed adding the name of libraries to the LIBS variable explicitly. This should be and is being taken care of by the configuration functions. This allows passing the correct library name to pkg-config, which does not need to be the name of the actual library file.
Split the combined cegui manager into seperate ones for old CEGUI versions below 0.8.0 and for CEGUI-0, starting at 0.8.0.
The cegui python extension for fife will automatically use the cegui version that corresponds to the installed PyCEGUI.
Also Fixed the linux scons script and translated the changed to the openbds and dawin scripts.
Merge branch 'master' into cegui_0.8