Mail: Reset PHPMailer properties between use.

Props xknown, martinkrcho, tykoted.

Built from https://develop.svn.wordpress.org/trunk@54529


git-svn-id: http://core.svn.wordpress.org/trunk@54084 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/pluggable.php

@@ -353,6 +353,8 @@ if ( ! function_exists( 'wp_mail' ) ) :
 		$phpmailer->clearAttachments();
 		$phpmailer->clearCustomHeaders();
 		$phpmailer->clearReplyTos();
+		$phpmailer->Body    = '';
+		$phpmailer->AltBody = '';
 
 		// Set "From" name and email.