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/texinputs/python.sty b/Doc/texinputs/python.sty
index f25041b..9fa56cd 100644
--- a/Doc/texinputs/python.sty
+++ b/Doc/texinputs/python.sty
@@ -833,7 +833,7 @@
\newcommand{\ctype}[1]{\texttt{#1}} % C struct or typedef name
\newcommand{\cdata}[1]{\texttt{#1}} % C variable, typically global
-\newcommand{\mailheader}[1]{\texttt{#1}}
+\newcommand{\mailheader}[1]{{\small\textsf{#1:}}}
\newcommand{\mimetype}[1]{{\small\textsf{#1}}}
% The \! is a "negative thin space" in math mode.
\newcommand{\regexp}[1]{%