1. emacs -Q -nw
2. M-x xterm-mouse-mode RET
3. Click once, then quickly move the cursor to a different word and click again.
4. Notice that the 2nd click was registered as a double click even
though the cursor moved.
5. Click once, and quickly perform step 3 again. Notice that the 3rd
click was registered as a triple click even though the cursor moved.

I've attached a patch that fixes this behaviour. It would be nice if it
worked with pixel positions rather than character positions, but I'm not
sure how to do that in a terminal Emacs.