Represent lines with non-empty lists.
We can do this because we removed lines with zero size.
Remove lines with zero size.
These lines would otherwise affect line numbering.
Do not re-export through the Plain module.
Move paragraphSpanBounds to the correct module.
Clarify comment about BiDi.
Correct comment about fragmentation.
Fix style: small Prelude imports.
Fix style: external vs internal imports.
Fix style: unnecessary do notation.
Fix style: white space in lambdas.
Fix style: white space around operators.
Fix style: white space in multi-line lists.
Fix style: white space in exports and imports.
Fix style: bullet points in comments.
Fix style: non-ASCII characters in comments.
Fix style: remove duplicate spaces.
Mark some lists as explicitly non-empty.