Add access modifiers to members and methods in `WP_Filesystem_Base`. Add magic `__get()` method for backwards compatibility.

See #27881, #22234.

Built from https://develop.svn.wordpress.org/trunk@28487


git-svn-id: http://core.svn.wordpress.org/trunk@28313 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Add access modifier (`public`) to methods in `WP_Filesystem_Direct`.

See #27881, #22234.

Built from https://develop.svn.wordpress.org/trunk@28488


git-svn-id: http://core.svn.wordpress.org/trunk@28314 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Add access modifier (`public`) to members and methods in `WP_Filesystem_FTPext`.

See #27881, #22234.

Built from https://develop.svn.wordpress.org/trunk@28489


git-svn-id: http://core.svn.wordpress.org/trunk@28315 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Add access modifier (`public`) to members and methods in `WP_Filesystem_ftpsockets`.

See #27881, #22234.

Built from https://develop.svn.wordpress.org/trunk@28490


git-svn-id: http://core.svn.wordpress.org/trunk@28316 1a063a9b-81f0-0310-95a4-ce76da25c4cd