Non-slashed $old_user_data->user_email in wp_insert_user causes user_activation_key to be unset

[emirpprime]

WordPress now allows apostrophes in email addresses, but the forgot password process for these users fails.

$data['user_activation_key'] in wp_insert_user() get's cleared when the $user_email !== $old_user_data->user_email comparison fails.
This is because $old_user_data is the "clean" data from the database, however wp_update_user() calls add_magic_quotes() on the user data it passes, causing apostrophes in email addresses to be slashed.

Process fails silently as there is no error when $data['user_activation_key'] is cleared in this flow, even though it is required for the forgot password system to function.

To replicate - register a user with an apostrophe in their email, use the lost password system from wp-login.php. An email will be sent/received, but the reset link is deemed invalid as there is no user_activation_key in the db.

Patch (about to be) attached to slash email only in $old_user_data. While this fixes the bug, it does raise the question of whether get_password_reset_key() should validate that the key is created directly as wp_update_user() errors don't give the granularity to tell us.