written before making the change.
Return 0 if all went well, and -1 if anything failed.
- EMACS_TTY_TABS_OK (struct emacs_tty *P) is false iff the kernel
+ EMACS_TTY_TABS_OK (struct emacs_tty *P) is false if the kernel
expands tabs to spaces upon output; in that case, there is no
advantage to using tabs over spaces. */