exec now uses the non-blocking IO constants from Configure. Thanks to Raphael for writing the dist module and to Andy for including it in Configure.
The decrypt filter has been enhanced to detect when it is executing as a dynamically linked module and if DEBUGGING is enabled. Thanks to Tim for providing the dynamic module test.
Tim provided a pile of bug fixes for decrypt.xs
Filter::call has been renamed Filter::Util::Call and the logic for installing it has been changed.
The workings of the filter method in Filter::Util::Call has been changed.