To ensure that this workaround runs even when Vim is started by a **separate tool** (such as git), I have this in my `~/.vimrc`:

    " Allow us to use Ctrl-s and Ctrl-q as keybinds
    silent !stty -ixon

    " Restore default behaviour when leaving Vim.
    autocmd VimLeave * silent !stty ixon

This has been working for me on Linux, GVim, Mac OS X and MacVim.

Caveats:

- On Windows, or any other OS lacking the `stty` command, the above will likely throw up errors every time Vim starts!  (`silent!` might mute that.)

- If your shell already had this TTY setting disabled, of course the `VimLeave` autocommand will turn it back on again!  Detecting and restoring the current settings is an advantage with @aPyDeveloper's approach.

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A combination of this and @aPyDeveloper's solution, which handles compatibility concerns under OS X and Windows, would be great to post up here and/or on the Wiki!

To avoid choosing between `stty -g` and `stty --save`, you could try the following test for just the `ix` option.  I can confirm it works on Linux, but I don't know about OS X:

    call system("stty -a | grep '\( \|^\)ixon\>' >/dev/null")
    let g:ix_at_startup = (v:shell_error == 0)