Move the styling for the HTML version of \mailheader into the CSS file.
In both the HTML and typeset versions of the documentation, add a colon
after the name of a mail header so that it is more easily distinguished
from other text.
diff --git a/Doc/perl/python.perl b/Doc/perl/python.perl
index 2f86de6..13e7aac 100644
--- a/Doc/perl/python.perl
+++ b/Doc/perl/python.perl
@@ -213,7 +213,7 @@
 sub do_cmd_email{
     return use_wrappers(@_[0], '<span class="email">', '</span>'); }
 sub do_cmd_mailheader{
-    return use_wrappers(@_[0], '<tt class="mimeheader">', '</tt>'); }
+    return use_wrappers(@_[0], '<span class="mailheader">', ':</span>'); }
 sub do_cmd_mimetype{
     return use_wrappers(@_[0], '<span class="mimetype">', '</span>'); }
 sub do_cmd_var{