Support different mouse pointers

[jaguililla]

It would be great to have extra SGR escape codes (like the ones for colored and styled underlines) to allow the mouse pointer to change on different text segments.

I.e.: switching to the 'pointer' mouse cursor when mouse tracking is enabled, and the cursor is over a text that act as a button.

If there is a way to achieve that now, could you please give some hints on how to proceed?

Thanks!

[kovidgoyal]

dup of #6711