~jaro/balkon

ref: ff8e9d3d0ef7236b5dbbc566203645483c56a9b9 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.