~jaro/balkon

ref: 9e3b0ec7fd4a92e3d2dba81cd00dadc4dfe4006c balkon/test/Data/Text/ParagraphLayout/PlainSpec.hs
Move non-public modules into Internal namespace.
Add test for RTL text.
Remove obsolete TODO.
Test line splitting with many runs.
Implement line breaking on code point boundaries.
Implement absolute line heights with half-leadings.
Use CSS-compatible line height settings.
Fix pretty printing for fragmented spans.
Upgrade Fragment to contain pen position.
Implement "plain" interface.
Create "plain" interface.