x/net/html/charset: Unclear license on w3c testdata

[bz2]

The README in html/charset/testdata states the tests come from the W3C but does not specify under which license go is reusing them, this makes redistribution in debian/ubuntu problematic.

Per:
http://www.w3.org/Consortium/Legal/2008/04-testsuite-copyright.html
We can just add a statement that the test files are licenced under the 3-clause BSD option.

Also, the link needs updating, the current is a 404 as it lacks /repository in the path.

So, README should be amended to something like:

"""
Test cases from:
http://www.w3.org/International/tests/repository/html5/the-input-byte-stream/results-basics

All *.html files copyright W3C and the following licence applies:
http://www.w3.org/Consortium/Legal/2008/03-bsd-license.html
"""

[ianlancetaylor]

http://golang.org/cl/8978

[gopherbot]

CL https://golang.org/cl/8978 mentions this issue.