Enables restoring of default values for pragma preferences. Fixes pref-setters that do not support 'nil' argument. Note that now both pref-getter and pref-setter have this 'nil' contract.
=============== Diff against System-mt.1179 ===============
Item was changed:
----- Method: PragmaPreference>>restoreDefaultValue (in category 'initialization') -----
+ "Try to send a reset request to the preference provider by setting the preference value to 'nil' to exploit the usual ifNil-pattern in the pragma-preference's getter.
+ Note that this reset is silent-by-design to be as fast as possible. If you want to send out notifications, try this:
+ self rawValue: self preferenceValue; notifyInformeeOfChange."
+ [[self rawValue: nil] valueSupplyingAnswer: true]
+ ifError: [:msg |
+ showln: 'Failed to reset pragma preference: ', provider printString, ' >> ', getter printString;
+ showln: msg].!
- "Pragma preferences preserve their current value"!