Eolian: Add an internal environment for class variables.

Eolian: Add an internal environment for class variables.

To reduce the invocations to strings conversions, we store the
classname, the Eo prefix in upper and lower cases in global variables.
The problem comes when we have to handle overriding functions. A lot of
conflicts between class base and class inheriting can happen.

The chosen solution is to create independent environments storing the
converted strings.