add quick search filter text field for encodings

[Karl-Philipp Richter]

in the dialogue where encodings can be added

ProblemType: Bug
DistroRelease: Ubuntu 15.04
Package: gedit 3.10.4-0ubuntu10
Uname: Linux 4.1.3-040103-generic x86_64
ApportVersion: 2.17.2-0ubuntu1.1
Architecture: amd64
CurrentDesktop: Unity
Date: Thu Jul 30 19:50:50 2015
InstallationDate: Installed on 2015-06-08 (52 days ago)
InstallationMedia: Ubuntu 14.04 LTS "Trusty Tahr" - Release amd64 (20140417)
ProcEnviron:
 TERM=xterm
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=de_DE.UTF-8
 SHELL=/bin/bash
SourcePackage: gedit
UpgradeStatus: Upgraded to vivid on 2015-06-09 (51 days ago)

[Sebastien Bacher (seb128)]

Thank you for taking the time to report this bug and helping to make Ubuntu better. The issue you are reporting is an upstream one and it would be nice if somebody having it could send the bug to the developers of the software by following the instructions at https://wiki.ubuntu.com/Bugs/Upstream/GNOME. If you have done so, please tell us the number of the upstream bug (or the link), so we can add a bugwatch that will inform us about its status. Thanks in advance.