*Title: No more $node variable in pagelayout.

*Documentation:
Global $node variable only exists in pagelayout template if it was set
by any other module which has run before fetching pagelayout template
and viewcache is disabled. Thus it is removed from pagelayout at all to
do not cause any confusions henceforth.
$module_result.node_id should be used to fetch current operated node in
a pagelayout template. Or you can pass any node id you need to fetch
through 'module_result' array from your own module to pagelayout as it
is shown in example below:

==============================
//// your_module.php file
...
$Result['some_node_id'] = $anyNodeIdYouNeed;
...

===============================
//// pagelayout.tpl file
...
{def $somenode = fetch( content, node, hash( node_id, $module_result.some_node_id ) )}
    ...
    {$somenode}
    ...