RexxUtil and pipe functions

RexxUtil has SysCreatePipe(), Unix only, and SysWaitNamedPipe(), Windows only, functions for pipe operations.

1.) Neither of the functions are of much use, that I can see, because there is no way to read and write to the pipes, or perform any other pipe operations.

2.) Both anonymous and named pipes are supported in both Windows and Unix.

We should add the appropriate functions to allow the user to work with the pipes and the functions should be unified so that they are platform independent.

Or, the other option, which might be more beneficial, would be to remove the two functions from RexxUtil and add a 'Pipe,' platform independent, extension with all the function needed to actually do something with pipes.