~jaro/balkon

ref: a9702991100ef8fc485ec47aed3d854c45e19dac 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.