Rework the TOC code so that it uses an a name= anchor

instead of `hx id=` (because the id= may pick up css unexpectedly.)

generate.c

@@ -1312,13 +1312,12 @@ text(MMIOT *f)
 static void
 printheader(Paragraph *pp, MMIOT *f)
 {
-    Qprintf(f, "<h%d", pp->hnumber);
     if ( f->flags & MKD_TOC ) {
-	Qprintf(f, " id=\"", pp->hnumber);
+	Qstring("<a name=\"", f);
 	mkd_string_to_anchor(T(pp->text->text), S(pp->text->text), Qchar, f, 1);
-	Qchar('"', f);
+	Qstring("\"></a>\n", f);
     }
-    Qchar('>', f);
+    Qprintf(f, "<h%d>", pp->hnumber);
     push(T(pp->text->text), S(pp->text->text), f);
     text(f);
     Qprintf(f, "</h%d>", pp->hnumber);

tests/toc.t

@@ -11,7 +11,8 @@ hi' \
 '<ul>
  <li><a href="#H1">H1</a></li>
 </ul>
-<h1 id="H1">H1</h1>
+<a name="H1"></a>
+<h1>H1</h1>
 
 <p>hi</p>'
 
@@ -22,14 +23,16 @@ try '-T -ftoc' 'toc item with link' \
   <li><a href="#H2.here">H2 here</a></li>
  </ul></li>
 </ul>
-<h2 id="H2.here"><a href="H2">H2</a> here</h2>'  
+<a name="H2.here"></a>
+<h2><a href="H2">H2</a> here</h2>'  
 
 try '-T -ftoc' 'toc item with non-alpha start' \
 '#1 header' \
 '<ul>
  <li><a href="#L1.header">1 header</a></li>
 </ul>
-<h1 id="L1.header">1 header</h1>'
+<a name="L1.header"></a>
+<h1>1 header</h1>'
 
 summary $0
 exit $rc