Awesome rewrite bug: the `page` query var was being set to `'/4'` in `$wp`. When cast to `int`, it returns `0` (Bless you, PHP). `WP_Query` calls `trim( $page, '/' )` when setting its own query var. The few places that were checking `page` before posts were queried now have sanity checks, so that these changes work without flushing rewrites.
Adds/updates unit tests.
Props wonderboymusic, dd32.
See #11694.
git-svn-id: https://develop.svn.wordpress.org/trunk@34492 602fd350-edb4-49c9-b593-d223f7449a82
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