+ Fixed file reading logic that leads to infinite loop.
+ Added SD_SAFE_DELETE* macros.
+ Fixed incorrect vertex buffer constructing data and logics.
+ Added Use function and renamed pointer variables.
+ Added Mesh::Use function.
+ Improved error handling logics and printed out more debug data.
+ Added codes for safely return system resources.
+ Implement dummy mesh rendering functions for checking Mesh and Material data validity.
- Renamed OnBeginBlock and OnEndBlock to OnOpenBlock and OnCloseBlock respectively.
+ Added renderer classes.
+ Corrected Material's Z-Write shift bit.
+ Implemented MeshRenderer::BeginRender function.
+ Improved RenderSystem class.
+ Uses MeshRenderer class for rendering quad mesh in main.cpp.