[BUGFIX] Forward uid to t3lib_BEfunc::getProcessedValue on creating differences

[BUGFIX] Forward uid to t3lib_BEfunc::getProcessedValue on creating differences

The behaviour to show differences of records basically was
copied from the history service. Since the history only works
on differences/deltas and not on fully stored records, no valid
uid can be used. However in the workspaces context each side
(live version and workspace version) has a valid uid.

By forwarding this data to t3lib_BEfunc::getProcessedValue,
hooks can use this valuable information.

Change-Id: Ifa1118eb84be8269e07618c4b35437d3762534e2
Fixes: #43070
Releases: 4.5, 4.6, 4.7, 6.0
Reviewed-on: http://review.typo3.org/16549
Reviewed-by: Oliver Hader
Tested-by: Oliver Hader