Update *_client_block documentation to match Roy's changes.

<h3>The New API Functions</h3>

<pre>

   int setup_client_block (request_rec *);

   int setup_client_block (request_rec *, int read_policy);

   int should_client_block (request_rec *);

   long get_client_block (request_rec *, char *buffer, int buffer_size);

</pre>

<li>Call <code>setup_client_block()</code> near the beginning of the request

    handler. This will set up all the neccessary properties, and

    will return either OK, or an error code. If the latter,

    the module should return that error code.

    the module should return that error code. The second parameter

    selects the policy to apply if the request message indicates a

    body, and how a chunked

    transfer-coding sho uld be interpreted. Choose one of

<pre>

    REQUEST_NO_BODY          Send 413 error if message has any body

    REQUEST_CHUNKED_ERROR    Send 411 error if body without Content-Length

    REQUEST_CHUNKED_DECHUNK  If chunked, remove the chunks for me.

    REQUEST_CHUNKED_PASS     Pass the chunks to me without removal.

</pre>

    In order to use the last two options, the caller MUST provide a buffer

    large enough to hold a chunk-size line, including any extensions.

<li>When you are ready to possibly accept input, call

    <code>should_client_block()</code>.

    buffer and its 

    size. It will put data into the buffer (not neccessarily the full

    buffer, in the case of chunked inputs), and return the length of

    the input block. When it is done reading, it will return 0, and

    the module should proceed.

    the input block. When it is done reading, it will

    return 0 if EOF, or -1 if there was an error.

</ol>