clang-format: Better understand Lambda poarameters.

Before:
  auto PointerBinding = [](const char * S) {};

After:
  auto PointerBinding = [](const char *S) {};

This fixes llvm.org/PR17618.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@193054 91177308-0d34-0410-b5e6-96231b3b80d8