-- Modify condition under which salloc execution delayed until moved to the

    foreground. Patch from Gerrit Renker, CSCS.
    a) salloc is not run in allocation-only (--no-shell) mode,
    b) stdin is from a terminal (tcgetattr does not return ENOTTY),
    c) salloc has been invoked from a login shell (not a nested one),
    d) salloc has been configured at compile-time to support background
       execution and is not currently in the background process group.