textview: Reset press counter if double/triple clicking on a different line

textview: Reset press counter if double/triple clicking on a different line

If we click close enough between lines, and with the maximum distances applied
by GtkGestureClick we could jump between lines when handling double/triple
click for word/line selection.

Ensure that the whole operation stays in the same line and reset the
gesture/counter if we do move between lines, so we start from scratch in the
new line.