Users: Provide a full user object when checking for a spammy multisite user

`is_user_spammy()` falls back to the current user if one is not provided. There is no current user during authentication, so the result is always `false`. Pass a user to fill the void.

Adds tests for `wp_authenticate_spam_check()`.

Props websupporter.
Fixes #36546.

Built from https://develop.svn.wordpress.org/trunk@37316


git-svn-id: http://core.svn.wordpress.org/trunk@37282 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/user.php

@@ -302,7 +302,7 @@ function wp_authenticate_spam_check( $user ) {
 		 * @param bool    $spammed Whether the user is considered a spammer.
 		 * @param WP_User $user    User to check against.
 		 */
-		$spammed = apply_filters( 'check_is_user_spammed', is_user_spammy(), $user );
+		$spammed = apply_filters( 'check_is_user_spammed', is_user_spammy( $user ), $user );
 
 		if ( $spammed )
 			return new WP_Error( 'spammer_account', __( '<strong>ERROR</strong>: Your account has been marked as a spammer.' ) );

wp-includes/version.php

@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.6-alpha-37315';
+$wp_version = '4.6-alpha-37316';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.