[wp-gsoc] [Summer of Code] #337: Only include support files if json_route URL matched

[Summer of Code]

#337: Only include support files if json_route URL matched
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 Reporter:  MikeSchinkel  |       Type:  enhancement
   Status:  new           |   Priority:  normal
Milestone:                |  Component:  JSON REST API
 Keywords:                |
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 The plugin is loading these files for every page load even if the JSON API
 is not used:

 {{{
 include_once( ABSPATH . WPINC . '/class-IXR.php' );
 include_once( ABSPATH . WPINC . '/class-wp-xmlrpc-server.php' );
 include_once( dirname( __FILE__ ) . '/lib/class-wp-json-server.php' );
 }}}

 Those files should not be loaded until after `json_api_loaded()` verifies
 that `/wp-json.php` was a matched route.

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Ticket URL: <https://gsoc.trac.wordpress.org/ticket/337>
Summer of Code <https://gsoc.trac.wordpress.org>
My example project