mesa: Bump version to 8.0 (devel)

Also update the release notes to mention that Mesa 8.0 implements
OpenGL 3.0.

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
diff --git a/docs/relnotes.html b/docs/relnotes.html
index 7e02172..1dd5442 100644
--- a/docs/relnotes.html
+++ b/docs/relnotes.html
@@ -13,7 +13,7 @@
 </p>
 
 <UL>
-<LI><A HREF="relnotes-7.12.html">7.12 release notes</A>
+<LI><A HREF="relnotes-8.0.html">8.0 release notes</A>
 <LI><A HREF="relnotes-7.11.html">7.11 release notes</A>
 <LI><A HREF="relnotes-7.10.3.html">7.10.3 release notes</A>
 <LI><A HREF="relnotes-7.10.2.html">7.10.2 release notes</A>