Do not resize the window on zoom
Fixes: #321 (closed)
I have tested it and couldn't find any regressions. After zooming in/out, the terminal window is not snapped to an integer number of columns and rows but I think this is preferred, as having the window size jump when zooming in/out would not be ideal. This is also consistent with behaviour of similar apps like emacs. The next time window is manually resized it will snap to the integer number of columns and rows.
I did not change the default behaviour of other similar functions. For example, showing/hiding the scroll bar still adjusts the window size and keeps the terminal screen size unchanged.