JimMakeChannel() function

Creates a channel for fh/fd/filename. If fh is not NULL, uses that as the channel (and sets AIO_KEEPOPEN). Otherwise fd must be >= 0, in which case it uses that as the channel. hdlfmt is a sprintf format for the filehandle. Anything with %ld at the end will do. mode is used for open or fdopen. Creates the command and sets the name as the current result. Returns the AioFile pointer on sucess or NULL on failure (only if fdopen fails).