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Unfill lines when generating release notes

The next release will use jemalloc

Closes #805

Missing words

Use tree-sitter-xml from crates.io

Link to relevant page in manual

Don't push empty positions when diffing lines

Ensure line splitting distinguishes "foo" and "foo\n"

We rely on being able to split lines and rejoin them to obtain the
original string. `str::lines()` in the Rust stdlib does not have this
property.

This was causing crashes in word-diffing on textual diffing, where
code paths differed on the number of lines they thought a string had.

This was broken in 8b84238.

Fixes #688.

It's not actually a 2x perf win

It's more like a 15% reduction in instruction count, which is still
nice.

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