Document how to do a SQL query in the background/parallel

Created a question for this http://drupal.stackexchange.com/questions/29815/using-call-user-func-arr...

Allows for syntax this this

$args = array(
  array(
    'type' => 'function',
    'call' => 'drupal_bootstrap',
    'args' => array(DRUPAL_BOOTSTRAP_FULL),
    'return' => '',
  ),
  array(
    'type' => 'function',
    'call' => 'db_query',
    'args' => array('SELECT MAX(wid) FROM {watchdog}'),
  ),
  array(
    'type' => 'function',
    'call' => 'db_result',
    'args' => array('last' => NULL),
  ),
  array(
    'type' => 'function',
    'call' => 'print_r',
    'args' => array('last' => NULL),
    'printed' => '',
  ),
);

$args = array(
  array(
    'type' => 'function',
    'call' => 'db_select',
    'args' => array('watchdog', 'w',),

  ),
  array(
    'type' => 'method',
    'call' => 'fields',
    'args' => array('w', array('wid')),
  ),
  array(
    'type' => 'method',
    'call' => 'orderBy',
    'args' => array('wid', 'DESC'),
  ),
  array(
    'type' => 'method',
    'call' => 'range',
    'args' => array(999, 1),
  ),
  array(
    'type' => 'method',
    'call' => 'execute',
    'args' => array(),
  ),
  array(
    'type' => 'method',
    'call' => 'fetchField',
    'args' => array(),
    'return' => '',
  ),
);

Following patch has been committed. Now I need to add it into the readme.

Fixed a minor error in the documentation
6.x - http://drupalcode.org/project/httprl.git/commitdiff/22f37769bad69cd6eba4...
7.x - http://drupalcode.org/project/httprl.git/commitdiff/cd845f3a2b72b0ba31b9...

The callback endpoint can now be done at database level bootstrap (full bootstrap currently). Copy httprl_caller.php to root dir... still need to workout some of the details.

Options this gives us:
- Running simple code no longer requires a full bootstrap (big speed improvement).
- Simple multi-step operations no long need a function wrapper.
- Include a file and run a function from it. Callbacks no longer need to be done in .module files.
- We can choose to bootstrap to a higher level and run code.

Thinking about this more and I think having the RPC callback be configurable so it can load from a file or hook boot is the best option. Having it backwards compatible is possible so I don't need a 2.x version now that I think about it.
#1558456: Create hook_boot endpoint

decided to scrap httprl_caller.php and go with hook_boot for faster execution times. Patch for readme has been committed.