[mediaqueries] Change p3 to dci-p3 per WG decision

Corresponding change in css-color:
436e62d

WG decision:
https://lists.w3.org/Archives/Public/www-style/2016Jun/0021.html

Author: zcorpan

mediaqueries/Overview.bs

@@ -1464,7 +1464,7 @@ Color Display Quality: the 'color-gamut' feature</h3>
 
 	<pre class='descdef mq'>
 	Name: color-gamut
-	Value: srgb | p3 | rec2020
+	Value: srgb | dci-p3 | rec2020
 	For: @media
 	Type: discrete
 	</pre>
@@ -1477,7 +1477,7 @@ Color Display Quality: the 'color-gamut' feature</h3>
 
 	Note: The query uses approximate ranges for a few reasons.
 	Firstly, there are a lot of differences in display hardware.
-	For example, a device might claim to support "Rec 2020",
+	For example, a device might claim to support "Rec.2020",
 	but actually renders a significantly lower range of the full gamut.
 	Secondly, there are a lot of different color ranges that different devices support,
 	and enumerating them all would be tedious.
@@ -1496,21 +1496,21 @@ Color Display Quality: the 'color-gamut' feature</h3>
 			Note: It is expected that the vast majority of color displays
 			will be able to return true to a query of this type.
 
-		<dt><dfn>p3</dfn>
+		<dt><dfn>dci-p3</dfn>
 		<dd>
 			The output device can support approximately the gamut
-			specified by the DCIP3 Color Space or more.
+			specified by the DCI P3 Color Space or more.
 
-			Note: The ''p3'' gamut is larger than and includes the ''srgb'' gamut.
+			Note: The ''dci-p3'' gamut is larger than and includes the ''srgb'' gamut.
 
-			Issue: Add ref for DCIP3.
+			Issue: Add ref for DCI P3.
 
 		<dt><dfn>rec2020</dfn>
 		<dd>
 			The output device can support approximately the gamut
 			specified by the ITU-R Recommendation BT.2020 Color Space or more.
 
-			Note: The ''rec2020'' gamut is larger than and includes the ''p3'' gamut.
+			Note: The ''rec2020'' gamut is larger than and includes the ''dci-p3'' gamut.
 
 			Issue: Add ref for BT.2020.
 	</dl>
@@ -1520,7 +1520,7 @@ Color Display Quality: the 'color-gamut' feature</h3>
 		in the range of DCI P3:
 
 		<pre class="lang-css">
-		@media (color-gamut: p3) { … }
+		@media (color-gamut: dci-p3) { … }
 		</pre>
 	</div>
 
@@ -1530,7 +1530,7 @@ Color Display Quality: the 'color-gamut' feature</h3>
 	As a result,
 	this feature is best used in an "ascending" fashion--
 	set a base value when ''(color-gamut: srgb)'' is true,
-	then override it if ''(color-gamut: p3)'' is true, etc.
+	then override it if ''(color-gamut: dci-p3)'' is true, etc.
 
 	Note: Some output devices,
 	such as monochrome displays,