[Orgmode] Problem with BEGIN_CENTER

[Baoqiu Cui]

It seems that the newly added feature BEGIN_CENTER only supports *one*
paragraph, i.e. only the first paragraph after BEGIN_CENTER will be
centered in exported HTML format.

For example, for the following lines in my Org file:

    #+BEGIN_CENTER
    Everything should be made as simple as possible, \\
    but not any simpler
    
    Repeat the above paragraph:
    
    Everything should be made as simple as possible, \\
    but not any simpler
    #+END_CENTER

I get the following HTML code, which, strictly speaking, contains a bug
because <p> is nested:

    <p style="text-align: center">
    Everything should be made as simple as possible, <br/>
    but not any simpler
    
    <p>
    Repeat the above paragraph:
    </p>
    <p>
    Everything should be made as simple as possible, <br/>
    but not any simpler
    </p>
    </p>

Is this the expected behavior?  I am trying to support this feature in
DocBook exporter, and would like to make BEGIN_CENTER work on multiple
paragraphs.

Baoqiu