Remove redundant checks in some update functions. Adds some readability/coding standards cleanup.

Props miqrogroove, azaozz.
Fixes #22828.

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Avoid database error when `include` or `exclude` is not really a `term_id`. Adds more unit tests.

Props kovshenin.
Fixes #11823.


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Avoids incorrect results when `url_to_postid()` checking is not strict enough. Adds a bunch of Unit Tests for `url_to_postid()', which is currently only tested lightly in some XML-RPC tests.

Props gcorne, gradyetc.
Fixes #20560.


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Twenty Fourteen: break long words in comment content (not just anchor text). Fixes #24890, props rickalee.
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Twenty Fourteen: add styling for medialement players, props celloexpressions. See #25209.
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