Next item structure works (#5380)

* Use "LEFT JOIN" to always fetch the item. Needed for update routines.

* New conversion routine that now covers every item

* Post update is now activated

* We now use a hash based upon RIPEMD-320 for content and activity

* The hash doesn't contain the plink anymore

* Legacy item fields are now "null"able

* New hash function for a server unique item hash

* Introduction of the legacy mode (usage of old item fields)

* Code simplification

* We don't need the "uri" fields anymore in item-activity and item-content

* Use the "created" and not the "received" date for the hash

* Avoiding several notices

* Some more warnings removed

* Improved uri-hash / Likes on Diaspora are now getting a creation date

* Corrected the post update version

* Ensure an unique uri-hash

* Don't delete orhaned item data at the moment

* Partly reworked, due to strange behaviour

* Some more parts reworked

* Using the uri currently seems to be more reliable

* Using the uri here as well

* Use the hash values again

* Grouped item fields in different categories

* Notices again

* use the gravity (we always should)

* Added hint for disabled post updates

* Notices ...

* Issue #5337: Personal notes are displayed again

* Use the gravity again

src/Core/System.php

@@ -212,7 +212,10 @@ EOT;
 	 */
 	public static function processID($prefix)
 	{
-		return uniqid($prefix . ':' . str_pad(getmypid() . ':', 8, '0') . ':');
+		// We aren't calling any other function here.
+		// Doing so could easily create an endless loop
+		$trailer = $prefix . ':' . getmypid() . ':';
+		return substr($trailer . uniqid('') . mt_rand(), 0, 26);
 	}
 
 	/// @todo Move the following functions from boot.php