Clarify that encoding tokens are scalar values

This replaces some occurrences of "code point" with "scalar value", since it might not be clear to passing readers that output streams from decoding and input streams to encoding cannot contain tokens which are surrogates.

Fixes #195.

encoding.bs

@@ -98,8 +98,8 @@ bitwise AND by "&", and bitwise OR by "|".
 
 <hr>
 
-<p>A <dfn id=concept-token>token</dfn> is a piece of data, such as a <a>byte</a>
-or <a>code point</a>.
+<p>A <dfn id=concept-token>token</dfn> is a piece of data, such as a <a>byte</a> or
+<a>scalar value</a>.
 
 <p>A <dfn id=concept-stream>stream</dfn> represents an ordered sequence of
 <a>tokens</a>. <dfn>End-of-stream</dfn> is a special
@@ -216,15 +216,24 @@ happening.
  <var>encoderDecoderInstance</var> is a <a for=/>decoder</a> instance, and "<code>fatal</code>"
  otherwise.
 
+ <li><p>Assert: if <var>encoderDecoderInstance</var> is an <a for=/>encoder</a> instance,
+ <var>token</var> is not a <a>surrogate</a>.
+
  <li><p>Let <var>result</var> be the result of running <var>encoderDecoderInstance</var>'s
  <a>handler</a> on <var>input</var> and <var>token</var>.
 
  <li><p>If <var>result</var> is <a>continue</a> or <a>finished</a>, return
  <var>result</var>.
 
- <li><p>Otherwise, if <var>result</var> is one or more
- <a>tokens</a>, <a>push</a>
- <var>result</var> to <var>output</var>.
+ <li>
+  <p>Otherwise, if <var>result</var> is one or more <a>tokens</a>:
+
+  <ol>
+   <li><p>Assert: if <var>encoderDecoderInstance</var> is a <a for=/>decoder</a> instance,
+   <var>result</var> does not contain any <a>surrogates</a>.
+
+   <li><p><a>Push</a> <var>result</var> to <var>output</var>.
+  </ol>
 
  <li>
   <p>Otherwise, if <var>result</var> is <a>error</a>, switch on <var>mode</var> and
@@ -858,6 +867,10 @@ different format here, to be able to represent ranges.)
 
  <p>The <a>get an encoding</a> algorithm is to be used to turn a <a>label</a> into an
  <a for=/>encoding</a>.
+
+ <p>Standards are to ensure that the streams they pass to the <a for=/>encode</a> and
+ <a>UTF-8 encode</a> algorithms are effectively scalar value streams, i.e., they contain no
+ <a>surrogates</a>.
 </div>
 
 <p>To <dfn export>decode</dfn> a byte stream <var>stream</var> using
@@ -898,7 +911,7 @@ fallback encoding <var>encoding</var>, run these steps:
  <a>prepend</a> the last byte of <var>buffer</var> to
  <var>stream</var>.
 
- <li><p>Let <var>output</var> be a code point <a for=/>stream</a>.
+ <li><p>Let <var>output</var> be a scalar value <a for=/>stream</a>.
 
  <li><p><a>Run</a> <var>encoding</var>'s
  <a for=/>decoder</a> with <var>stream</var> and <var>output</var>.
@@ -918,7 +931,7 @@ these steps:
  <li><p>If <var>buffer</var> does not match 0xEF 0xBB 0xBF,
  <a>prepend</a> <var>buffer</var> to <var>stream</var>.
 
- <li><p>Let <var>output</var> be a code point <a for=/>stream</a>.
+ <li><p>Let <var>output</var> be a scalar value <a for=/>stream</a>.
 
  <li><p><a>Run</a> <a>UTF-8</a>'s
  <a for=/>decoder</a> with <var>stream</var> and <var>output</var>.
@@ -930,7 +943,7 @@ these steps:
 steps:
 
 <ol>
- <li><p>Let <var>output</var> be a code point <a for=/>stream</a>.
+ <li><p>Let <var>output</var> be a scalar value <a for=/>stream</a>.
 
  <li><p><a>Run</a> <a>UTF-8</a>'s
  <a for=/>decoder</a> with <var>stream</var> and <var>output</var>.
@@ -945,7 +958,7 @@ steps:
      -->
 
 <ol>
- <li><p>Let <var>output</var> be a code point stream.
+ <li><p>Let <var>output</var> be a scalar value stream.
 
  <li><p>Let <var>potentialError</var> be the result of <a>running</a>
  <a>UTF-8</a>'s <a for=/>decoder</a> with <var>stream</var>, <var>output</var>, and
@@ -958,8 +971,8 @@ steps:
 
 <hr>
 
-<p>To <dfn export>encode</dfn> a code point stream <var>stream</var> using
-encoding <var>encoding</var>, run these steps:
+<p>To <dfn export>encode</dfn> a scalar value stream <var>stream</var> using encoding
+<var>encoding</var>, run these steps:
 
 <ol>
  <li><p>Assert: <var>encoding</var> is not <a>replacement</a>, <a>UTF-16BE</a> or
@@ -979,9 +992,8 @@ encoding <var>encoding</var>, run these steps:
 [[URL]]
 [[HTML]]
 
-<p>To <dfn export>UTF-8 encode</dfn> a code point stream <var>stream</var>,
-return the result of <a lt=encode for=/>encoding</a>
-<var>stream</var> using encoding <a>UTF-8</a>.
+<p>To <dfn export>UTF-8 encode</dfn> a scalar value stream <var>stream</var>, return the result of
+<a lt=encode for=/>encoding</a> <var>stream</var> using encoding <a>UTF-8</a>.
 
 
 
@@ -3278,6 +3290,7 @@ Adam Rice,
 Alan Chaney,
 Alexander Shtuchkin,
 Allen Wirfs-Brock,
+Andreu Botella,
 Aneesh Agrawal,
 Arkadiusz Michalski,
 Asmus Freytag,