Bump the trunk version to 4.0.0svn.

Differential Revision: https://reviews.llvm.org/D21821

llvm-svn: 275827
diff --git a/llvm/docs/conf.py b/llvm/docs/conf.py
index 224cca1..d7e9e2d 100644
--- a/llvm/docs/conf.py
+++ b/llvm/docs/conf.py
@@ -48,9 +48,9 @@
 # built documents.
 #
 # The short X.Y version.
-version = '3.9'
+version = '4.0'
 # The full version, including alpha/beta/rc tags.
-release = '3.9'
+release = '4.0'
 
 # The language for content autogenerated by Sphinx. Refer to documentation
 # for a list of supported languages.