clang-format: Understand more lambda return types.

Before:
  auto a = [&b, c ](D * d) -> D * {}

After:
 auto a = [&b, c](D* d) -> D* {}

git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@222534 91177308-0d34-0410-b5e6-96231b3b80d8