Log Message:
Update ruby-nokogiri to 1.6.8.1

=== 1.6.8.1 / 2016-10-03

==== Dependency License Notes

Removes required dependency on the `pkg-config` gem. This dependency
was introduced in v1.6.8 and, because it's distributed under LGPL, was
objectionable to many Nokogiri users (#1488, #1496).

This version makes `pkg-config` an optional dependency. If it's
installed, it's used; but otherwise Nokogiri will attempt to work
around its absence.

=== 1.6.8 / unreleased

==== Security Notes

[MRI] Bundled libxml2 is upgraded to 2.9.4, which fixes many security issues. \ 
Many of these had previously been patched in the vendored libxml 2.9.2 in the \ 
1.6.7.x branch, but some are newer.

See these libxml2 email posts for more:

* https://mail.gnome.org/archives/xml/2015-November/msg00012.html
* https://mail.gnome.org/archives/xml/2016-May/msg00023.html

For a more detailed analysis, you may care to read Canonical's take on these \ 
security issues:

* http://www.ubuntu.com/usn/usn-2994-1

[MRI] Bundled libxslt is upgraded to 1.1.29, which fixes a security issue as \ 
well as many long-known outstanding bugs, some features, some portability \ 
improvements, and general cleanup.

See this libxslt email post for more:

* https://mail.gnome.org/archives/xslt/2016-May/msg00004.html

==== Features

Several changes were made to improve performance:

* [MRI] Simplify NodeSet#to_a with a minor speed-up. (#1397)
* XML::Node#ancestors optimization. (#1297) (Thanks, Bruno Sutic!)
* Use Symbol#to_proc where we weren't previously. (#1296) (Thanks, Bruno Sutic!)
* XML::DTD#each uses implicit block calls. (Thanks, @glaucocustodio!)
* Fall back to the `pkg-config` gem if we're having trouble finding the system \ 
libxml2. This should help many FreeBSD users. (#1417)
* Set document encoding appropriately even on blank document. (#1043) (Thanks, \ 
@batter!)

==== Bug Fixes

* [JRuby] fix slow add_child (#692)
* [JRuby] fix load errors when deploying to JRuby/Torquebox (#1114) (Thanks, \ 
@atambo and @jvshahid!)
* [JRuby] fix NPE when inspecting nodes returned by NodeSet#drop (#1042) \ 
(Thanks, @mkristian!)
* [JRuby] fix nil attriubte node's namespace in reader (#1327) (Thanks, \ 
@codekitchen!)
* [JRuby] fix Nokogiri munging unicode characters that require more than 2 bytes \ 
(#1113) (Thanks, @mkristian!)
* [JRuby] allow unlinking an unparented node (#1112, #1152) (Thanks, @esse!)
* [JRuby] allow Fragment parsing on a frozen string (#444, #1077)
* [JRuby] HTML `style` tags are no longer encoded (#1316) (Thanks, @tbeauvais!)
* [MRI] fix assertion failure while accessing attribute node's namespace in \ 
reader (#843) (Thanks, @2potatocakes!)
* [MRI] fix issue with GCing namespace nodes returned in an xpath query. (#1155)
* [MRI] Ensure C strings are null-terminated. (#1381)
* [MRI] Ensure Rubygems is loaded before using mini_portile2 at installation. \ 
(#1393, #1411) (Thanks, @JonRowe!)
* [MRI] Handling another edge case where the `libxml-ruby` gem's global \ 
callbacks were smashing the heap. (#1426). (Thanks to @bbergstrom for providing \ 
an isolated test case!)
* [MRI] Ensure encodings are passed to Sax::Parser xmldecl callback. (#844)
* [MRI] Ensure default ns prefix is applied correctly when reparenting nodes to \ 
another document. (#391) (Thanks, @ylecuyer!)
* [MRI] Ensure Reader handles non-existent attributes as expected. (#1254) \ 
(Thanks, @ccutrer!)
* [MRI] Cleanup around namespace handling when reparenting nodes. (#1332, #1333, \ 
#1444) (Thanks, @cuttrer and @bradleybeddoes!)
* unescape special characters in CSS queries (#1303) (Thanks, @twalpole!)
* consistently handle empty documents (#1349)
* Update to mini_portile2 2.1.0 to address whitespace-handling during patching. \ 
(#1402)
* Fix encoding of xml node namespaces.
* Work around issue installing Nokogiri on overlayfs (commonly used in Docker \ 
containers). (#1370, #1405)

==== Other Notes

* Removed legacy code remaining from Ruby 1.8.x support.
* Removed legacy code remaining from REE support.
* Removing hacky workarounds for bugs in some older versions of libxml2.
* Handling C strings in a forward-compatible manner, see \ 
https://github.com/ruby/ruby/blob/v2_2_0/NEWS#L319