cure warning CS0253: Possible unintended reference comparison; to get a value comparison, cast the right hand side to type 'System.Delegate'

A value comparison is what we want here. The C# equality operator will exactly do what is wanted here:
check if a function is already in the list and, if yes, remove it.

cf http://msdn.microsoft.com/en-us/library/system.delegate.op_equality(v=vs.100).aspx

Change-Id: I64e85006140fca3d81e733f13d7e8cf17bfaa336