Extend character clipping by grouping it with spaces

Summary:
Group spaces following any non-wide character with the character. This
allows for rendering ambiguous characters with wide glyphs without
clipping them. Characters are still clipped when followed by another
visible character.

{F6591346}

BUG 401298

Test Plan:
* Display: `⛰ ⛩ `
and/or:
* Install Font Awesome or other font with square icons in Private Use
  Area
* Pick some icons using KCharSelect or similar tool (or copy this:
  `     `)
* Put space after each icon and display them in Konsole

**Actual result:**
Only left half of icons is rendered
**Expected result:**
Full icon should be rendered (it can be clipped on top or bottom though)

Reviewers: #konsole, hindenburg

Reviewed By: #konsole, hindenburg

Subscribers: hindenburg, konsole-devel

Tags: #konsole

Differential Revision: https://phabricator.kde.org/D18784