Don't use variable variables in `get_terms()`.

See #27881.

Built from https://develop.svn.wordpress.org/trunk@28736


git-svn-id: http://core.svn.wordpress.org/trunk@28550 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Don't use variable variables in `WP_Query::get_posts()`.

See #27881.

Built from https://develop.svn.wordpress.org/trunk@28737


git-svn-id: http://core.svn.wordpress.org/trunk@28551 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Don't use variable variables in `WP_Comment_Query::query()`.

See #27881.

Built from https://develop.svn.wordpress.org/trunk@28738


git-svn-id: http://core.svn.wordpress.org/trunk@28552 1a063a9b-81f0-0310-95a4-ce76da25c4cd