Inherit NCollection_Buffer from Standard_Transient, do not use incomplete NCollection_Handle.
OpenGl_Context, add methods ActiveProgram(),BindProgram()
to manage currently active GLSL program.
Add method ::ToUseVbo().
OpenGl_ShaderProgram, setup locations of pre-defined vertex attributes
occVertex, occNormal, occTexCoord, occColor before linkage.
Remove methods OpenGl_ShaderProgram::Bind(), ::BindWithVariables()
and ::Unbind() - OpenGl_Context::BindProgram() should be used instead.
Introduce class OpenGl_VertexBufferCompat, which emulates VBO
behavior on systems without VBO (compatibility with broken OpenGL drivers on Windows).
OpenGl_PrimitiveArray - use OpenGl_VertexBufferCompat when VBO is unavailable,
remove duplicated code. Use OpenGl_VertexBuffer::HasNormalAttribute()
method to activate lighting.
OpenGl_Text - use OpenGl_VertexBufferCompat, eliminate duplicated code.
Changes in OpenGl_VertexBuffer, drop methods BindFixed()/UnbindFixed().
Superseded by new methods BindAllAttributes()/UnbindAllAttributes()
which handle active GLSL program, when it is set.
NCollection_BaseCollection class, relevant header files, and macro DEFINE_BASECOLLECTION removed.
Hence methods Assign() from other compatible (via inheritance of BaseCollection) collections are not available any more, as well as base Iterator class.
All methods of Iterator classes are made non-virtual, allowing their inline expansion for better performance.
OCCT-specific operators new and delete added to collection classes and removed from iterator classes.
