Marcel Taeumel uploaded a new version of System to project The Trunk:
http://source.squeak.org/trunk/System-mt.765.mcz

==================== Summary ====================

Name: System-mt.765
Author: mt
Time: 28 August 2015, 10:02:11.682 am
UUID: b40396ff-9c0f-bb46-9317-779e2ccb6448
Ancestors: System-topa.764

For consistency, also support setting and restoring regular preference within the scope of a block. Like flags (i.e. boolean preferences) support it.

=============== Diff against System-topa.764 ===============

Item was added:
+ ----- Method: Preferences class>>setPreference:toValue:during: (in category 'get/set') -----
+ setPreference: prefSymbol toValue: anObject during: aBlock
+ 
+ 	(self valueOfPreference: prefSymbol) in: [:previous |
+ 		self setPreference: prefSymbol toValue: anObject.
+ 		aBlock ensure: [self setPreference: prefSymbol toValue: previous]].!