Implement direct output to stdout and stderr

[cspiel]

Try to implement an option (--output-direct) that circumvents the usual
redirections that OMake applies to any command.

At its current state the change already allows for interesting tests like,
for example,

section
        OMakeFlags(--output-direct)

        .PHONY: mirar
        mirar:
                w3m $(HOME)/src/omake.git/doc/html/omake-doc.html

What is missing is an output of the active rule and the command line itself.
This is what --output-normal prints in case of the command outputting
anything. For planned option --output-direct I think this information
ought to be printed always.