[css-mixins-1][css-values-5] Move the definition of <syntax> to V&U 5…

…, since we'll be using it in multiple places.

css-mixins-1/Overview.bs

@@ -585,91 +585,4 @@ Issue: Should we indeed use {{CSSNestedDeclarations}} for this purpose?
 	should probably not be a regular {{CSSStyleDeclaration}},
 	since only custom properties
 	and the '@function/result' descriptor
-	are relevant.
-
-<!-- Big Text: appendix
-
- ███▌  ████▌  ████▌  █████▌ █    █▌ ████▌  ████ █     █
-▐█ ▐█  █▌  █▌ █▌  █▌ █▌     █▌   █▌ █▌  █▌  ▐▌   █   █ 
-█▌  █▌ █▌  █▌ █▌  █▌ █▌     ██▌  █▌ █▌  █▌  ▐▌    █ █  
-█▌  █▌ ████▌  ████▌  ████   █▌▐█ █▌ █▌  █▌  ▐▌     █   
-█████▌ █▌     █▌     █▌     █▌  ██▌ █▌  █▌  ▐▌    █ █  
-█▌  █▌ █▌     █▌     █▌     █▌   █▌ █▌  █▌  ▐▌   █   █ 
-█▌  █▌ █▌     █▌     █████▌ █▌   ▐▌ ████▌  ████ █     █
--->
-
-Appendix: The <<syntax>> Production {#syntax}
-=============================================
-
-The <<syntax>> production represents a [=syntax definition=],
-which may be used to impose a type
-on [=function parameters=],
-[=function dependencies=],
-or [=custom function=] return values.
-
-<pre class="prod def" nohighlight>
-	<dfn><<syntax-type>></dfn> = angle | color | custom-ident | image | integer |
-		length | length-percentage | number |
-		percentage | resolution | string | time |
-		url | transform-function
-	<dfn><<syntax-combinator>></dfn> = '|'
-	<dfn><<syntax-multiplier>></dfn> = [ '#' | '+' ]
-	<dfn><<syntax-component-name>></dfn> = '<' <<syntax-type>> '>' | <<custom-ident>>
-	<dfn><<syntax-component>></dfn> = <<syntax-component-name>> <<syntax-multiplier>>? |
-		'<' transform-list '>'
-	<dfn><<syntax>></dfn> = '*' | <<syntax-component>> [ <<syntax-combinator>> <<syntax-component>> ]+
-</pre>
-
-A <<syntax-component>> consists of either a <<syntax-type>>,
-which maps to one of the [=supported syntax component names=];
-or a <<custom-ident>>, which represents any [=keyword=].
-Additionally,
-a <<syntax-component>> may contain a [[css-properties-values-api-1#multipliers|multiplier]],
-which indicates a [=list=] of values.
-
-Note: This means that <code>&lt;length&gt;</code>
-	and <code>length</code> are two different types:
-	the former describes a <<length>>,
-	whereas the latter describes a [=keyword=] <code>length</code>.
-
-Multiple <<syntax-component>>s may be [[css-properties-values-api-1#combinator|combined]]
-with a <code>|</code> <<delim-token>>,
-causing the syntax components to be matched
-against a value
-in the specified order.
-
-<div class='example'>
-	<xmp class='lang-css'>
-		<percentage> | <number> | auto
-	</xmp>
-
-	The above, when parsed as a <<syntax>>,
-	would accept <<percentage>> values,
-	<<number>> values,
-	as well as the keyword <code>auto</code>.
-</div>
-
-<div class='example'>
-	<xmp class='lang-css'>
-	red | <color>
-	</xmp>
-
-	The [=syntax definition=] resulting from the above <<syntax>>,
-	when used as a grammar for [=parse|parsing=],
-	would match an input <code>red</code> as an [=identifier=],
-	but would match an input <code>blue</code> as a <<color>>.
-</div>
-
-The <code>*</code> <<delim-token>> represents the [=universal syntax definition=].
-
-The <code>&lt;transform-list&gt;</code> production
-is a convenience form equivalent to <code>&lt;transform-function&gt;+</code>.
-<span class=note>Note that <code>&lt;transform-list&gt;</code> may not
-	be followed by a <<syntax-multiplier>>.</span>
-
-[=Whitespace=] is not allowed
-between the angle bracket <<delim-token>>s (<code>&lt;</code> <code>&gt;</code>)
-and the <<syntax-type>> they enclose,
-nor is [=whitespace=] allowed to precede a <<syntax-multiplier>>.
-
-Note: The [=whitespace=] restrictions also apply to <code>&lt;transform-list&gt;</code>.
+	are relevant.