Fix up the HTML generated for envdesc and macrodesc environments.

Make it possible for the user to tell the difference.  ;-)

Doc/perl/ltxmarkup.perl

@@ -56,7 +56,7 @@ sub do_env_envdesc{
     my $env = ltx_next_argument();
     my $params = ltx_process_params(ltx_next_argument());
     return "\n<dl class=envdesc>"
-         . "\n<dt><b><tt class=environment>&#92;$env</tt></b>"
+         . "\n<dt><tt>&#92;begin{<b class=environment>$env</b>}</tt>"
          . "\n    $params"
 	 . "\n<dd>"
 	 . $_