External Libraries: Upgrade PHPMailer to version 6.8.1.

This is a minor maintenance release.

Note: WordPress core does not include PHPMailer's DSN class, as it is not particularly relevant for WP.

References:
* [https://github.com/PHPMailer/PHPMailer/releases/tag/v6.8.1 PHPMailer 6.8.1 release notes]
* [PHPMailer/PHPMailer@v6.8.0...v6.8.1 Full list of changes in PHPMailer 6.8.1]

Follow-up to [50628], [50799], [51169], [51634], [51635], [52252], [52749], [52811], [53500], [53535], [53917], [54427], [54937], [55557].

Props jrf, Synchro.
Fixes #59238.

git-svn-id: https://develop.svn.wordpress.org/trunk@56484 602fd350-edb4-49c9-b593-d223f7449a82

Author: SergeyBiryukov

src/wp-includes/PHPMailer/PHPMailer.php

@@ -750,7 +750,7 @@ class PHPMailer
      *
      * @var string
      */
-    const VERSION = '6.8.0';
+    const VERSION = '6.8.1';
 
     /**
      * Error severity: message only, continue processing.
@@ -795,7 +795,7 @@ class PHPMailer
      * The maximum line length supported by mail().
      *
      * Background: mail() will sometimes corrupt messages
-     * with headers headers longer than 65 chars, see #818.
+     * with headers longer than 65 chars, see #818.
      *
      * @var int
      */

src/wp-includes/PHPMailer/SMTP.php

@@ -35,7 +35,7 @@ class SMTP
      *
      * @var string
      */
-    const VERSION = '6.8.0';
+    const VERSION = '6.8.1';
 
     /**
      * SMTP line break constant.
@@ -704,7 +704,7 @@ public function close()
      * Send an SMTP DATA command.
      * Issues a data command and sends the msg_data to the server,
      * finalizing the mail transaction. $msg_data is the message
-     * that is to be send with the headers. Each header needs to be
+     * that is to be sent with the headers. Each header needs to be
      * on a single line followed by a <CRLF> with the message headers
      * and the message body being separated by an additional <CRLF>.
      * Implements RFC 821: DATA <CRLF>.
@@ -732,7 +732,7 @@ public function data($msg_data)
         $lines = explode("\n", str_replace(["\r\n", "\r"], "\n", $msg_data));
 
         /* To distinguish between a complete RFC822 message and a plain message body, we check if the first field
-         * of the first line (':' separated) does not contain a space then it _should_ be a header and we will
+         * of the first line (':' separated) does not contain a space then it _should_ be a header, and we will
          * process all lines before a blank line as headers.
          */