Performance improvement
Update Ars Technica
Fix a regression that broke the compare books tool when used outside the book editor. Fixes #1321975 [Unhandled exception when comparing epub books](https://bugs.launchpad.net/calibre/+bug/1321975)
Fix regression that sometimes caused incorrect syntax highlighting when non-breaking spaces/typographic hyphens are present in the text. Fixes #1321317 [Edit book: Wrong hilighting in spaces](https://bugs.launchpad.net/calibre/+bug/1321317)
Initial implementation of C code to speedup tinycss tokenization

Needs testing.
Testing for the C tokenizer
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Add tokenizer tests into the --test-build test suite
Kindle APNX: Add calculation using pagebreak tag.
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Add a paragraph on the Live CSS panel to the manual
Live CSS: Handle updates more gracefully when the cursor is in a CSS editor or a <style> tag

We prevent incorrect data from being returned by ensuring that updates
are not done while the preview panel is being refreshed. We also only
update data after the event loop has run for some time after a refresh.
Live CSS: Prevent unnecessary refreshes when simply moving the cursor around in the same tag
Add an option to hide the book rating in the cover browser (Preferences->Look & Feel->Cover Browser). Fixes #1319476 [Disable Rating in Cover Browser](https://bugs.launchpad.net/calibre/+bug/1319476)
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fix equality.
fix indentation.
fix fiding pagebreak tags.
page apnx algorithm to search for all tags with pagebreak in them.