Add README.version for external/clang.

(cherry picked from commit 979abd17ed9cb3b0a1e3064e61990c8415139448)

Change-Id: I554462a494ce45a34b4ec86c4152c0aaa9a3cf8d
diff --git a/README.version b/README.version
new file mode 100644
index 0000000..cb69cbc
--- /dev/null
+++ b/README.version
@@ -0,0 +1,4 @@
+URL: http://llvm.org/git/clang.git
+Version: Rolling from upstream + cherry-picks
+BugComponent: 117395
+Owners: srhines, android-llvm