title: Hibernate hbm2ddl.auto=update doesn't update column definitions in MySQL
body: <p>I'm trying to update existing table with hbm2ddl.auto = update. <br><br>There is several columns in several tables where database column definitions changes from declaration in entities. Like</p>
  
  <pre><code>@Column(name="mycolumn", nullable=false, length=10)
  private Long mycolumn;
  </code></pre>
  
  <p>and </p>
  
  <blockquote>
    <p>'mycolumn' bigint(20) not null default 0</p>
  </blockquote>
  
  <p>in MySQL.</p>
  
  <p>Why hbm2ddl doesn't update such things? And is it possible to force such update?
  I want to say hbm2ddl to remove default value of column and change length of type.</p>