unix function

[John W. Eaton]

I see that octave-forge includes a unix.m file that emulates the
Matlab unix function.  For Unix-like systems, this is implemented in
terms of the sysmtem function and for Windows systems there is a
separate file that does nothing.  Is that really what isunix does in
Matlab on Windows systems?  I can't find anything that says so in the
documentation.  In any case, given that we have an isunix function, I
think we should have just one version of unix.m, so I propose adapting
the version from octave-forge.

Comments?

jwe