严重BUG：当分词内容中包含单独的A字母时，这个A字母会被分词器扔掉

GET /_analyze
{
  "analyzer" : "ik_smart",
  "text" : "我们A A制"
}
{
  "tokens": [
    {
      "token": "我们",
      "start_offset": 0,
      "end_offset": 2,
      "type": "CN_WORD",
      "position": 0
    },
    {
      "token": "制",
      "start_offset": 5,
      "end_offset": 6,
      "type": "CN_CHAR",
      "position": 1
    }
  ]
}