OpenGl_Buffer - added new class as a base for OpenGl_VertexBuffer, OpenGl_IndexBuffer, OpenGl_TextureBuffer.
OpenGl_TextureBufferArb has been renamed to OpenGl_TextureBuffer.
OpenGl_FrameBuffer - added initializers taking vec2i instead of (int,int) for dimensions.
Graphic3d_RenderTransparentMethod has been extended by Graphic3d_RTM_DEPTH_PEELING_OIT,
which is handled by OpenGl_LayerList::renderTransparent().
OpenGl_FrameBuffer::Init() now does not silently ignore unknown color attachment format and return failure.
OpenGl_FrameBuffer::InitWrapper() - added constructor wrapping existing color textures.
v3d/transparency/oit: test case added