[swig] omit superfluous virtual method definitions
[swig] omit superfluous virtual method definitions

http://www.swig.org/Doc1.3/Modules.html

Trying to reduce size of generated source code.
opensim-org/opensim-core,opensim-org/opensim-core,opensim-org/opensim-core,opensim-org/opensim-core,opensim-org/opensim-core,opensim-org/opensim-core,opensim-org/opensim-core