clang-format: Prefer not to put lambdas on a single line.

Before:
  string abc =
      SomeFunction(aaaaaaaaaaaaa, aaaaa,
                   []() { SomeOtherFunctioooooooooooooooooooooooooon(); });

After:
  string abc = SomeFunction(aaaaaaaaaaaaa, aaaaa, []() {
    SomeOtherFunctioooooooooooooooooooooooooon();
  });

llvm-svn: 215197