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();
  });

git-svn-id: http://llvm.org/svn/llvm-project/cfe/trunk@215197 91177308-0d34-0410-b5e6-96231b3b80d8