Automatically convert pipe constructs to a Unix pipeline

[arunisaac]

Automatically convert pipe constructs to a Unix pipeline. This is only possible in the special case when an stdout type output of one command is connected to the stdin of a later command. Nevertheless, this could be a powerful feature to improve performance by never touching the disk. For cases when a Unix pipeline is undesirable, for example when such a pipeline may run out of memory, we should provide an option to disable this automatic conversion.

Thanks to @pjotrp for suggesting this feature.