The implementation in Writer has been read-only since initial CVS
import, so adapt com.sun.star.text.textfield.SetExpression to
implementation.

Change-Id: I70cdd5d0a44cb86426f533c00f86874e8dde8b87
SERVICE: /UCR/com/sun/star/text/textfield/SetExpression
 incompatible change: Field 11 ('VariableName') of r1 is not longer a
 property of this SERVICE in r2
 incompatible change: Field 11 ('VariableName') of r2 is a new
 property compared to this SERVICE in r1 and is not 'optional'