clang-format: Fix incorrect lambda recognition.

Before:
  std::unique_ptr<int[]> foo() {}

After:
  std::unique_ptr<int []> foo() {}

Also, the formatting could go severely wrong after such a function
before.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@199817 91177308-0d34-0410-b5e6-96231b3b80d8