+3. Read/Draw Buffer changes
+
+ The business of setting the current read/draw buffers in Mesa 4.0.x
+ was complicated. It's much simpler now in Mesa 4.1.
+
+ Here are the changes:
+
+ - Renamed ctx->Color.DrawDestMask to ctx->Color._DrawDestMask
+ - Removed ctx->Color.DriverDrawBuffer
+ - Removed ctx->Pixel.DriverReadBuffer
+ - Removed ctx->Color.MultiDrawBuffer
+ - Removed ctx->Driver.SetDrawBuffer()
+ - Removed swrast->Driver.SetReadBuffer().
+ - Added ctx->Color._DrawDestMask - a bitmask of FRONT/BACK_LEFT/RIGHT_BIT
+ values to indicate the current draw buffers.
+ - Added ctx->Pixel._ReadSrcMask to indicate the source for pixel reading.
+ The value is _one_ of the FRONT/BACK_LEFT/RIGHT_BIT values.
+ - Added ctx->Driver.DrawBuffer() and ctx->Driver.ReadBuffer().
+ These functions exactly correspond to glDrawBuffer and glReadBuffer calls.
+ Many drivers will set ctx->Driver.DrawBuffer = _swrast_DrawBuffer and
+ leave ctx->Draw.ReadBuffer NULL.
+ DRI drivers should implement their own function for ctx->Driver.DrawBuffer
+ and use it to set the current hardware drawing buffer. You'll probably
+ also want to check for GL_FRONT_AND_BACK mode and fall back to software.
+ Call _swrast_DrawBuffer() too, to update the swrast state.
+ - Added swrast->Driver.SetBuffer().
+ This function should be implemented by all device drivers that use swrast.
+ Mesa will call it to specify the buffer to use for span reading AND
+ writing and point/line/triangle rendering.
+ There should be no confusion between current read or draw buffer anymore.
+ - Added swrast->CurrentBuffer to indicate which color buffer to read/draw.
+ Will be FRONT_LEFT_BIT, BACK_LEFT_BIT, FRONT_RIGHT_BIT or BACK_RIGHT_BIT.
+ This value is usually passed to swrast->Driver.SetBuffer().
+
+
+4. _mesa_create_context() changes. This function now takes a pointer to
+ a __GLimports object. The __GLimports structure contains function
+ pointers to system functions like fprintf(), malloc(), etc.
+ The _mesa_init_default_imports() function can be used to initialize
+ a __GLimports object. Most device drivers (like the DRI drivers)
+ should use this.
+
+
+5. In tnl's struct vertex_buffer, the field "ProjectedClipCoords"
+ has been replaced by "NdcPtr" to better match the OpenGL spec's
+ terminology.
+
+
+6. Since GL_EXT_stencil_two_side has been implemented, many of the
+ ctx->Stencil fields are now 2-element arrays. For example,
+ "GLenum Ref" is now "GLenum Ref[2]" The [0] elements are the front-face
+ values and the [1] elements are the back-face values.
+ ctx->Stencil.ActiveFace is 0 or 1 to indicate the current face for
+ the glStencilOp/Func/Mask() functions.
+ ctx->Stencil.TestTwoSide controls whether or not 1 or 2-sided stenciling
+ is enabled.
+
+
+7. Removed ctx->Polygon._OffsetAny. Removed ctx->Polygon.OffsetMRD.
+
+
+8. GLfloat / GLchan changes:
+
+ - Changed ctx->Driver.ClearColor() to take GLfloat[4] instead of GLchan[4].
+ ctx->Color.ClearColor is now GLfloat[4] too.
+ - Changed ctx->Driver.AlphaRef() to take GLfloat instead of GLchan.
+ - ctx->Color.AlphaRef is now GLfloat.
+ - texObj->BorderColor is now GLfloat[4]. texObj->_BorderChan is GLchan[4].
+
+ This is part of an effort to remove all GLchan types from core Mesa so
+ that someday we can support 8, 16 and 32-bit color channels dynamically
+ at runtime, instead of at compile-time.
+
+
+9. GLboolean ctx->Tranform.ClipEnabled[MAX_CLIP_PLANES] has been replaced
+ by GLuint ctx->Transform.ClipPlanesEnabled. The later is a bitfield.
+
+
+10. There's a new matrix_stack type in mtypes.h used for the Modelview,
+ Projection, Color and Texcoord matrix stacks.
+
+
+11. The ctx->Current.* fields have changed a lot. Now, there's a
+ ctx->Current.Attrib[] array for all vertex attributes which matches
+ the NV vertex program conventions.
+
+