docs: move old relnotes to _extra directory

These aren't built, so they won't get copied out into the public folder
unless we put is inside the _extra folder.

This has been broken all since the conversion to Sphinx, whoops!

Reviewed-by: Eric Engestrom <eric@igalia.com>
Reviewed-by: Marcin Ślusarz <marcin.slusarz@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/21956>

docs/_extra/relnotes/6.2

@@ -0,0 +1,51 @@
+
+                           Mesa 6.2 release notes
+
+                              October 2, 2004
+
+                              PLEASE READ!!!!
+
+
+
+Introduction
+------------
+
+Mesa uses an even/odd version number scheme like the Linux kernel.
+Odd numbered versions (such as 6.1) designate new developmental releases.
+Even numbered versions (such as 6.2) designate stable releases.
+
+
+This release primarily just fixes bugs found in the Mesa 6.1 release.
+See the VERSIONS file for details.
+
+
+ToDo: PBO for polygon stipple, convolution filter, etc.
+
+
+
+Known Issues
+------------
+
+The GL_EXT_pixel_buffer_object extension isn't fully implemented for
+functions like glPolygonStipple, glConvolutionFilter, glColorTable,
+etc.  The important functions like glRead/DrawPixels, glTex[Sub]Image,
+and glBitmap work with PBOs.
+
+
+
+Driver			Status
+----------------------	---------------------
+XMesa (Xlib)		implements OpenGL 1.5
+OSMesa (off-screen)	implements OpenGL 1.5
+Glide (3dfx Voodoo1/2)	implements OpenGL 1.3
+SVGA			implements OpenGL 1.3
+Wind River UGL		implements OpenGL 1.3
+Windows/Win32		implements OpenGL 1.5
+DJGPP			implements OpenGL 1.5
+GGI			implements OpenGL 1.3
+BeOS			implements OpenGL 1.5
+Allegro			needs updating
+D3D			needs updating
+
+
+----------------------------------------------------------------------