Deals with a special topic: While frequencies at VATSIM/flightsim are usually set in 25kHz spacing, some ATC stations (radar) require 8.33kHz tuning.
The now made extension handles this and allows to listen to a voice room even if the corresponding frequency is not exactly tuned in.
Example: EKDK_CTR 135,270 but needs to be tuned in as 135,275
The new compare is implemented using "multimethods" described in the book Advanced C++ Programming Styles and Idioms by James Coplien.
First, the isA method is used to determine which of the values being compared is the most general. (For example, CLength is more general than CAltitude.)
Then the compareImpl method is called on the most general value, with the other value as an argument.
If there is not a direct inheritance relation between the two values (or they are the same class) then the comparison is invalid and a assert is triggered.
Still required but unwanted overloaded DBus operator in aviomodulator.h - no compilation without them. Need to be removed.
Enabled more classes for DBus.
