clang-format: [Java] Support generics with "?".

Before:
  @Override
  public Map < String,
          ? > getAll() {
    // ...
  }

After:
  @Override
  public Map<String, ?> getAll() {
    // ...
  }

This fixes llvm.org/PR21454.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@221109 91177308-0d34-0410-b5e6-96231b3b80d8