[indie-ui-context] boolean media queries should probably use 1/0 values, not on/off

https://dvcs.w3.org/hg/IndieUI/raw-file/default/src/indie-ui-context.html#userMediaSettings
sections 2.3 (User Media Settings) and 2.4 (Screen Reader Settings)
define a number of media features with on | off values.

I tend to think these should probably have 1 | 0 values instead,
to match the other boolean-like media features in
http://www.w3.org/TR/css3-mediaqueries/ such as color, monochrome,
and grid.  Using <integer> values 1 or 0 allows authors to use more
boolean-like syntax:
  (screenreader)
rather than having to write:
  (screenreader: on)
since the media queries spec treats zero values as a special case in
http://www.w3.org/TR/css3-mediaqueries/#media1 .

-David

-- 
𝄞   L. David Baron                         http://dbaron.org/   𝄂
𝄢   Mozilla                          https://www.mozilla.org/   𝄂
             Before I built a wall I'd ask to know
             What I was walling in or walling out,
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