title: mysqldump with utf8 can not export the right emojis string
body: <p>I am using MySQL 5.5.29, utf8mb4 charset, there is a table user containing a field <code>nickname</code> with value hex <code>F09F988EF09F988E</code> that translates to the emojis .</p>
  
  <p>Now open MySQL console, and execute:</p>
  
  <hr>
  
  <pre><code>set names utf8mb4;
  select nickname, hex(nickname) from user;
  </code></pre>
  
  <hr>
  
  <pre><code>nickname | hex(nickname)
  ---------+-----------------
      | F09F988EF09F988E
  </code></pre>
  
  <hr>
  
  <p>And then execute:</p>
  
  <pre><code>mysqldump --default-character-set=utf8 -utest -ptest test_dev user &gt; user.sql
  </code></pre>
  
  <p>Check the <code>user.sql</code> and find the nickname display <code>??</code> which hex string is 3f</p>
  
  <p>So, how can mysqldump with UTF8 export the right emojis string? </p>
  
  <hr>
  
  <p>btw, the database charset envionments configured as follow:
  show variables like 'character_set_%':</p>
  
  <pre><code>'character_set_client', 'utf8mb4'
  'character_set_connection', 'utf8mb4'
  'character_set_database', 'utf8mb4'
  'character_set_filesystem', 'binary'
  'character_set_results', 'utf8mb4'
  'character_set_server', 'utf8mb4'
  'character_set_system', 'utf8'
  'character_sets_dir', '/data/mysql/share/charsets/'
  </code></pre>