EMI: Make SCXTrack behave like MP3Track in regards to isPlaying
GRIM: Use exact string search when searching for shadow sectors.

Fixes shadows in set st.
GRIM: Test model center position instead of origin in shouldDrawShadow. Fixes #741
Merge pull request #907 from somaen/fixPS2Audio

EMI: Make SCXTrack behave like MP3Track in regards to isPlaying
MATH: Make inverseTranslate and inverseRotate methods of Matrix4 const.
EMI: Allow vertices to be associated with multiple joints.
EMI: Allow nil to be passed to volume in PlayLoadedSound
EMI: Add support for clamping sprite textures and repeating other textures.
GRIM/EMI: fix compiler warning

- remove unused variable
Merge pull request #910 from JoseJX/FixGLTextureParams

EMI: Clamp sprites, repeat other textures.
Merge pull request #930 from Akz-/grim-shadows-fix

GRIM: Shadow fixes
Merge pull request #932 from Akz-/emi-skinning-fix

EMI: Fix vertex skinning
EMI: Free more memory properly
GRIM/EMI: Do not check if _chores is null as it does not matter
EMI: Remove doublefreeing of materials.

I think there are cases where things are not all freed, but something else
is going wrong causing issues here.
DEBIAN: disable enabling shaders for now
GRIM/EMI: Cleanup

- add override to overridden functions
- make sure that all overridden functions are virtual
- make local functions protected
EMI: Clear depth buffer before starting to draw the Overworld

- all actors of the Overworld should cover any non-Overworld drawings
- Overworld actors need to use the depth buffer so that e.g. the
pause screen is drawn above the inventory

- this fixes issue #927 (inventory is drawn above background of pause
  or menu screen)
EMI: Change frustum parameters for Overworld actors

- lower the distance to the near plane of the frustum for Overworld
  and change the other parameters accordingly

- this makes the following actors visible:
 - background of directions to Pegnose Pete's house (issue #869)
 - Murray in the murray_go easter egg
 - the trophies during the diving contest (upper left corner)
 - the screenshots for the save games (still with the wrong texture)