Update to LTS 6.49 changes

[pwolanin]

Applying the changes from D6 LTS using cherry pick from
https://github.com/d6lts/drupal.git

The relevant commits I applied from that repo were:

commit 01cfc83aa6a483654cfed589a50696671014d89b
Author: David Snopek <dsnopek@gmail.com>
Date:   Wed Jan 16 11:49:04 2019 -0600

    Backport of fixes from SA-CORE-2019-002

commit 8becc15c9d5508216ba4a46a16fef9c2361b63f0
Author: David Snopek <dsnopek@gmail.com>
Date:   Wed Jan 16 11:50:34 2019 -0600

    Update version number to 6.48

commit e45f482c5fe4bb9127f4aa5cda85f16f6a60a9aa
Author: David Snopek <dsnopek@gmail.com>
Date:   Wed Jan 16 14:56:33 2019 -0600

    Fix Drush issues from SA-CORE-2019-002

commit 5f5351b88ceed9b790f476888152ce677c99ab70
Author: David Snopek <dsnopek@gmail.com>
Date:   Wed Jan 16 15:04:20 2019 -0600

    Update version number to 6.49

Plus updating the CHANGELOG.txt