[clang-format] Fix lines regression in clang-format.py

Summary:
This patch fixes a regression after https://reviews.llvm.org/rL305665,
which updates the structure of the `lines` variable.

Reviewers: djasper

Reviewed By: djasper

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D37011

git-svn-id: svn://svn.chromium.org/llvm-project/cfe/trunk/tools/clang-format@311456 0b72dbe1-c17f-4bc7-b9db-2b4152be0356
diff --git a/clang-format.py b/clang-format.py
index 2412566..187125e 100644
--- a/clang-format.py
+++ b/clang-format.py
@@ -62,7 +62,7 @@
 
   # Determine range to format.
   if vim.eval('exists("l:lines")') == '1':
-    lines = vim.eval('l:lines')
+    lines = ['-lines', vim.eval('l:lines')]
   elif vim.eval('exists("l:formatdiff")') == '1':
     with open(vim.current.buffer.name, 'r') as f:
       ondisk = f.read().splitlines();