Add additional text encoding aliases per Encoding Standard

Additional aliases are required by the Encoding Standard beyond those
present in ICU 4.6.

R=jshin@chromium.org
BUG=277025

Review URL: https://codereview.chromium.org/32673006

git-svn-id: svn://svn.chromium.org/blink/trunk@160158 bbb929c8-8fbe-4397-9dbb-9b2b20218538