Documentation and docstrings for the 'cmd'-as-sequence
usage of popenX functions in os and popen2 on unix. 
All texts are a variation on the following:
    On \UNIX, \var{cmd} may be a sequence, in which
case arguments will be passed directly to the program
without shell intervention (as with
\function{os.spawnv()}.  If \var{cmd} is a string it
will be passed to the shell (as with
\function{os.system()}).

See also 888380 for an older patch addressing the same
issue.  If this patch is applied, that tracker item
should be closed too.