SBX as Run

Added October 2012

When set within an SBX, any files opened subsequently within that SBX will be auto-closed when this SBX returns. The flag name comes from the idea that in some kinds of menu architectures, you may use SBXs to execute programs that might otherwise have been executed with RUN. The difference is that in the case of a RUN, on exit, all files (and most other resources) are automatically closed or released, whereas with SBXs, files opened in the SBX remain open and accessible to the parent, as well as to other SBXs called by the parent or by the original SBX.