Setting cursor shape in terminals.

[Random832]

I have a script (modified from the one posted in discussion section of
Emacs Wiki linked below) for changing the cursor shape depending on
whether I am in a read-only buffer or in overwrite mode. It's set to box
for read-only, hbar for overwrite, bar otherwise.

It works well in the GUI, but I would like to extend it to terminal
mode. My terminal (this seems to be something of a standard) allows the
escape sequence ESC [ n SPC q, where n is:
- 0 default
- 1 box blinking
- 2 box non-blinking
- 3 hbar blinking
- 4 hbar non-blinking
- 5 bar [extension of iTerm2]
- 6 bar non-blinking

I don't know enough to know where to even look for how to add a way for
Emacs to emit these escape sequences whenever the cursor changes.

http://emacswiki.org/emacs/ChangingCursorDynamically