clang-format: Detect weird macro lambda usage.

Before:
  void f() {
    MACRO((const AA & a) { return 1; });
  }

After:
  void f() {
    MACRO((const AA &a) { return 1; });
  }

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@203551 91177308-0d34-0410-b5e6-96231b3b80d8