Allow manual specification of parent

A menu item's parent is derived from the structure of the path which forces people to construct complex paths to create menu structure. Provide a way to separate menu structure from path so that path can be used purely to specify the path.

A menu item's parent is derived from the structure of the path using the following code:

$parent = substr($parent, 0, strrpos($parent, '/'));

That line does not give modules the freedom to create structured menus when the path does not use a structure as occurs in taxonomy. The following taxonomy path could be three levels deep in a menu but cannot be decoded that way:
taxonomy/term/65

As an example, taxonomy_menu has to replace the taxonomy style path, taxonomy/term/65, with a duplicate path to generate a structured menu. The following path is an example of a taxonomy_menu path and creates a huge number of problems because a node cannot have multiple paths:
taxonomy_term/12/32/54/65

The ideal, in the taxonomy_menu case, is to use existing paths and define the menu structure another way. The flexibility will let us path purely as a path and define the menu structure independently. To achieve the independence, I added one extra test to allow manual specification of a parent via a 'parent' attribute.

I changed following code. The code logic looks a bit backward with the !isset and performing the complex case first.

if (!isset($item['pid']))
	{
	// Parent's location has not been customized, so figure it out using the path.
	$parent = $item['path'];
	if ($parent)
		{
		do
			{
			$parent = substr($parent, 0, strrpos($parent, '/'));
			}
		while ($parent && !isset($_menu['path index'][$parent]));
		}
	$pid = $parent ? $_menu['path index'][$parent] : 1;
	$_menu['items'][$mid]['pid'] = $pid;
	}
else
	{
	$pid = $item['pid'];
	}

I reversed the order for simplicity.

if (isset($item['pid']))
	{
	$pid = $item['pid'];
	}
else
	{
	// Parent's location has not been customized, so figure it out using the path.
	$parent = $item['path'];
	if ($parent)
		{
		do
			{
			$parent = substr($parent, 0, strrpos($parent, '/'));
			}
		while ($parent && !isset($_menu['path index'][$parent]));
		}
	$pid = $parent ? $_menu['path index'][$parent] : 1;
	$_menu['items'][$mid]['pid'] = $pid;
	}

Next I added one extra test for $item['parent']:

if (isset($item['pid']))
	{
	$pid = $item['pid'];
	}
elseif(isset($item['parent']) and isset($_menu['path index'][$item['parent']]))
	{
	$pid = $_menu['path index'][$item['parent']];
	$_menu['items'][$mid]['pid'] = $pid;
	}
else
	{
	// Parent's location has not been customized, so figure it out using the path.
	$parent = $item['path'];
	if ($parent)
		{
		do
			{
			$parent = substr($parent, 0, strrpos($parent, '/'));
			}
		while ($parent && !isset($_menu['path index'][$parent]));
		}
	$pid = $parent ? $_menu['path index'][$parent] : 1;
	$_menu['items'][$mid]['pid'] = $pid;
	}