Transcode the HTML part of incoming email into UTF-8 as well

Summary:
D1093 did this for just the text/plain part of incoming
email.  Most text/html parts choose to either use entity encoding
//or// are already UTF-8, thus obviating the need to transcode the
HTML part.  However, this is not always the case, and leads to dropped
messages, by way of:

```
EXCEPTION: (Exception) Failed to JSON encode value (phacility#5: Malformed UTF-8 characters, possibly incorrectly encoded): Dictionary value at key "html" is not valid UTF8, and cannot be JSON encoded: [snip HTML part of message content]```

Generalize the charset transcoding to not apply to just the text/plain part, but
both text/plain and text/html parts.

Test Plan:
Fed in a Windows-1252-encoded text/html part with 0x92
bytes in it; verified that $content only contained valid UTF-8 after
this change.

Reviewers: #blessed_reviewers, epriestley

Reviewed By: #blessed_reviewers, epriestley

Subscribers: Korvin, epriestley

Differential Revision: https://secure.phabricator.com/D18776

Author: Alex Vandiver

scripts/mail/mail_handler.php

@@ -35,16 +35,19 @@
 $parser = new MimeMailParser();
 $parser->setText(file_get_contents('php://stdin'));
 
-$text_body = $parser->getMessageBody('text');
-
-$text_body_headers = $parser->getMessageBodyHeaders('text');
-$content_type = idx($text_body_headers, 'content-type');
-if (
-  !phutil_is_utf8($text_body) &&
-  (preg_match('/charset="(.*?)"/', $content_type, $matches) ||
-   preg_match('/charset=(\S+)/', $content_type, $matches))
-) {
-  $text_body = phutil_utf8_convert($text_body, 'UTF-8', $matches[1]);
+$content = array();
+foreach (array('text', 'html') as $part) {
+  $part_body = $parser->getMessageBody($part);
+  $part_headers = $parser->getMessageBodyHeaders($part);
+  $content_type = idx($part_headers, 'content-type');
+  if (
+    !phutil_is_utf8($part_body) &&
+    (preg_match('/charset="(.*?)"/', $content_type, $matches) ||
+     preg_match('/charset=(\S+)/', $content_type, $matches))
+  ) {
+    $part_body = phutil_utf8_convert($part_body, 'UTF-8', $matches[1]);
+  }
+  $content[$part] = $part_body;
 }
 
 $headers = $parser->getHeaders();
@@ -57,10 +60,7 @@
 
 $received = new PhabricatorMetaMTAReceivedMail();
 $received->setHeaders($headers);
-$received->setBodies(array(
-  'text' => $text_body,
-  'html' => $parser->getMessageBody('html'),
-));
+$received->setBodies($content);
 
 $attachments = array();
 foreach ($parser->getAttachments() as $attachment) {