The pointer passing for display options is deprecated. This removes the
excess casting as the EDA_FRAME didn't need the base call with no value.
All requests for display options are now returned const and are updated
with a Set() routine after modification.
In Gerbview, this resolves an issue where the display options were not
stored because it was receiving the NULL from EDA_FRAME.
The standard DIM() macro was not typesafe as it happily deferred errors
to runtime that can be caught at compile time. Replacing it with a
generic C++11 constexpr allows for typecasting, comparison and compile
time error checking.
Seth Hillbrand
Jeff Young
Seth Hillbrand