mime: don't accept single-quoted strings in media type parameter values
Fix an old bug where media type parameter values could be escaped by
either double quotes (per the spec) or single quotes (due to my bug).
The original bug was introduced by me in git rev
90e4ece3
(https://golang.org/cl/
4430049) in April 2011 when adding more tests
from http://greenbytes.de/tech/tc2231/ and misinterpreting the
expected value of test "attwithfntokensq" and not apparently thinking
about it enough.
No known spec or existing software produces or expects single quotes
around values. In fact, it would have be a parsing ambiguity if it
were allowed: the string `a=', b='` could parse as two keys "a" and
"b" both with value "'", or it could be parse as a single key "a" with
value "', b=".
Fixes #11291
Change-Id: I6de58009dd47dcabb120b017245d237cb7b1e89a
Reviewed-on: https://go-review.googlesource.com/17136
Reviewed-by: Russ Cox <rsc@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>