[css-page-floats] Fix markup

Author: tabatkins

css-page-floats/Overview.bs

@@ -199,7 +199,7 @@ And some more text</p>
 
 <pre class="propdef">
   Name: float
-  Value: block-start | block-end | inline-start | inline-end | snap-block | snap-inline | left | right | top | bottom | none
+  Value: block-start | block-end | inline-start | inline-end | snap-block | <<snap-block()>> | snap-inline | <<snap-inline()>> | left | right | top | bottom | none
   Initial: none
   Applies to: all elements.
   Inherited: no
@@ -288,8 +288,14 @@ And some more text&lt;/p>
     Behave like block-end or inline-end depending on the float
     containing block’s 'direction' and 'writing-mode'.
 
-  <dt><dfn>snap-block(&lt;length> [, start | end | near ]?)</dfn>
+  <dt><dfn function>snap-block()</dfn>
   <dd>
+      The ''snap-block()'' function is defined as:
+
+      <pre class='prod'>
+        snap-block() = snap-block( <<length>> , [ start | end | near ]? )
+      </pre>
+
       Has no effect if the element is an <a>inline float</a>.
 
       If the element is a <a>page float</a>, it makes the element float to the
@@ -306,10 +312,16 @@ And some more text&lt;/p>
       the start and the end, end wins.
 
   <dt><dfn>snap-block</dfn>
-  <dd>same as <code>snap-block(2em, near)</code>
+  <dd>Behaves as <code>snap-block(2em, near)</code>
 
-  <dt><dfn>snap-inline(&lt;length> [, left | right | near ]?)</dfn>
+  <dt><dfn function>snap-inline()</dfn>
   <dd>
+      The ''snap-inline()'' function is defined as:
+
+      <pre class='prod'>
+        snap-inline() = snap-inline( <<length>> , [ left | right | near ]? )
+      </pre>
+
       Has no effect if the element is an <a>inline float</a>.
 
       If the element is a <a>page float</a>, it makes the element float to the