Extending to right neighbors is intended for text meters with an
overlong content, so the whole text is shown if possible.
Multi column meters, like the combined memory and swap meter, position
its text depending on the given total width; keep the position to the
original assigned header slot.
Short term resolution for #796
Use the same width for each sub meter to align with CPU meter.
Currently if the total width is even, so it does not split exactly into
2 equal parts plus 1 (for the middle space character column), the extra
column is added to the second meter width.
Closes: #783
