This patch automatically configures reindexing of the search table when the
table is dropped and recreated.

The DomDocument::saveHtml() method will properly urlencode() values in the
a[@href] attributes when saving. This patch allows for the sanitization
while also allowing the variable replacement system to work properly with
the sanitized values.

When using the php mail() function, the To: header encoded in the Mail_mime
library was not properly transferred to the $to variable passed to the mail
backend. The mail() function will add its own To: header which will
mimic the received destination address.

This patch ensures that the $to parameter is properly encoded.

When using call_user_func_array arguments should be passed by reference in order to allow callable receive them by reference (only defining callable to receive data by reference is not enough).

This patch will help ensure that if a ticket is not reopened on a message
(perhaps because of a out-of-office auto-reply from an enduser), then the
closing agent on a closed ticket should not be cleared.

This fixes an issue where text scrubbed with the new balancing system would
receive a leading ' <div>' if the text started with a leading whitespace.

Thanks, @torohill

This fixes a strange issue where the first field of a custom form stapled to
a ticket is not populated with data sourced from the API.

9ae01bf2 turned off HTML balancing, however,
quoted response removal will create unbalanced HTML. That HTML will be
stored unbalanced and will require extra processing when displayed on the
ticket thread.

This patch adds balancing support using libxml if enabled, which will
balance HTML without corrupting the HTML like htmLawed will with balancing
enabled.

* Reindexing did not properly flush the last batch of items to the search
  therefore reindexing would always miss the last few items.
* Creating a new html thread entry with inline images resulted in empty
  search content
* HTML tag stripping in HtmlThreadBody::getSearchable() would result in
  missing white space between some words, resulting in poor searchable
  content

Which seems to be used by recent versions of Andriod OS. It appears to be a
synonym of `multipart/related`

Also, fix roundtrip encryption if the form name changes (which is based on a
user's session), and avoid saving a NULL value if the password is not
changed when a form is updated.

If navigating back to the ticket queue (after closing a ticket, for
instance), return to the queue previously viewed.

(Most notably is the mail from Outlook, which embeds block elements inside
of <font> elements.)

If the email address in use by the end user is not valid, display a warning
on the ticket view page. This allows an agent to easily flag potential spam
or correct a legitimate email address before sending a response and
receiving a bounce notice.

This allows detection of some incorrectly-typed email addresses before
tickets, users, and agents are created.

Preserve text formatting on the internal note posted to a new ticket by
staff if HTML thread is disabled.

This is necessary for some mail clients which indicate encoding in GB2312
but actually use GBK encoding.

If osTicket was improperly or incompletely upgraded, then some tables may
exist which should otherwise not exist. This patch assists the upgrade
process by dropping the tables which should not exist prior to adding or
renaming tables.

This correctly handles a bounce message with the following layout:

multipart/report; report-type=delivery-status
    multipart/alternative; differences=Content-Type
        text/plain; charset="us-ascii"
        text/html; charset="us-ascii"
    message/delivery-status
    message/rfc822

Fixes #1854