Canonical meta tag for paginated posts incorrect with ugly permalinks

[peterwilsoncc]

Following [34496] canonical URLs of paginated posts with ugly permalinks are incorrect.

Page http://example.com/?p=1&page=2
Canonical meta tag: <link rel="canonical" href="http://example.com/?p=1/2" />.

Going the canonical URL loads the first page.

Note: title updated to reference meta tag

[peterwilsoncc]

34890.diff​ corrects canonical URL for paginated posts:

• Never adds pagination for the first page
• Uses the page querystring if pretty permalinks are not set

Adapted from the code in _wp_link_page.

[peterwilsoncc]

34890.2.diff​ includes unit tests for paginated posts both with and without pretty permalinks.

Let me know if the tests needs rewriting, moving or both, it's my first attempt at unit tests.

[jorbin]

@wonderboymusic, @joostdevalk - this was introduced in [34496] which both of you worked on, can you take a look?

[dd32]

In 36096:

Canonical: Output correct canonical links for paged posts when not using pretty permalinks.

Props peterwilsoncc.
Fixes #34890

[dd32]

In 36103:

Canonical: Output correct canonical links for paged posts when not using pretty permalinks.

Merges [36096] to the 4.4 branch.
Props peterwilsoncc.
Fixes #34890.