Bump the trunk version to 9.0.0svn

llvm-svn: 351320
diff --git a/libcxx/docs/conf.py b/libcxx/docs/conf.py
index 50b372c..e88b2d3 100644
--- a/libcxx/docs/conf.py
+++ b/libcxx/docs/conf.py
@@ -47,9 +47,9 @@
 # built documents.
 #
 # The short X.Y version.
-version = '8.0'
+version = '9.0'
 # The full version, including alpha/beta/rc tags.
-release = '8.0'
+release = '9.0'
 
 # The language for content autogenerated by Sphinx. Refer to documentation
 # for a list of supported languages.