Replace missing math images with Unicode

www/old-psyntax.html

@@ -235,7 +235,7 @@ An <tt>import</tt> form now has the following syntax:
 
 
    <TABLE><TR><TD nowrap align="left">
-<i>spec</i></TD><TD nowrap align="center"><img src="math/site/0.gif" alt="<graphic>"></TD><TD nowrap align="left"><i>id</i></TD></TR><TR><TD nowrap align="left">
+<i>spec</i></TD><TD nowrap align="center">=</TD><TD nowrap align="left"><i>id</i></TD></TR><TR><TD nowrap align="left">
   </TD><TD nowrap align="center">|</TD><TD nowrap align="left"><tt>(only</tt> <i>spec</i> <i>id</i>*<tt>)</tt></TD></TR><TR><TD nowrap align="left">
   </TD><TD nowrap align="center">|</TD><TD nowrap align="left"><tt>(except</tt> <i>spec</i> <i>id</i>*<tt>)</tt></TD></TR><TR><TD nowrap align="left">
   </TD><TD nowrap align="center">|</TD><TD nowrap align="left"><tt>(add-prefix</tt> <i>spec</i> <i>id</i><tt>)</tt></TD></TR><TR><TD nowrap align="left">
@@ -469,7 +469,7 @@ reexports, e.g.,
 
 (module&nbsp;m2&nbsp;(a)&nbsp;(import&nbsp;m1))<br>
 
-(let&nbsp;()&nbsp;(import&nbsp;m2)&nbsp;a)&nbsp;<img src="math/site/1.gif" alt="<graphic>">&nbsp;3</tt>
+(let&nbsp;()&nbsp;(import&nbsp;m2)&nbsp;a)&nbsp;&rarr;&nbsp;3</tt>
 <p><li>Fixed a bug in the portable expander that prevented use of "hidden"
 top-level definitions in the output of a macro, e.g.:
 
@@ -491,13 +491,13 @@ top-level definitions in the output of a macro, e.g.:
 
 (counter&nbsp;get&nbsp;bump&nbsp;17)<br>
 
-(get)&nbsp;<img src="math/site/1.gif" alt="<graphic>">&nbsp;17<br>
+(get)&nbsp;&rarr;&nbsp;17<br>
 
 (bump&nbsp;4)<br>
 
-(get)&nbsp;<img src="math/site/1.gif" alt="<graphic>">&nbsp;21<br>
+(get)&nbsp;&rarr;&nbsp;21<br>
 
-hidden&nbsp;<img src="math/site/1.gif" alt="<graphic>">&nbsp;unbound&nbsp;error</tt>
+hidden&nbsp;&rarr;&nbsp;unbound&nbsp;error</tt>
 <p><li>An incompatible change to the expander has been
 made to reduce the loss of source information when one macro generates
 another macro definition: List and vector structure in the subexpression