This allows attaching multiple shader programs, processing the entire
screen as texture. Chaining shaders works, each shader will use
the output of the previous shader as input.
- Removed some unused member variables.
- The BBGE_BUILD_WIDESCREEN define is now gone.
- Added an TiXMLDocument cache to prevent parsing the same file
once for each entity on the map with the same skeletal.
- Removed Lua func entity_warpToPathStart, which was essentially a no-op
because Entity::followingPath was always NULL. Removed related code.
- Set texture wrap only when required.
(Some changes taken from https://bitbucket.org/mattbierner/ios-aquaria,
special thanks for changeset 72d6460d9e60)
