This will find (forwards or backwards) but preserve the existing selection.
Presently if the current selection is a zero-width selection (i.e. caret) then we still preserve it. This might not be desired, but one could imagine “extend selection” used with a regular expression which use a look-around assertion (resulting in zero-width matches).
When we need to work on a paragraph (reflow, unwrap, select, etc.) we now extend upward until we see a blank line, and likewise move downward until there is a blank line.
This is related to issue #154.
There is a bunch of functions that deal with the logical column count and these now all count code points with the “east asian width” (unicode) property set as two columns.
This closes issue #206.
