Added support for optional explanation parameter to the \versionadded

macro.

Refactored do_cmd_versionadded() and do_cmd_versionchanged() to do most
of the work in a helper function, with the do_cmd_*() wrappers just supplying
a portion of the replacement text.

Doc/perl/python.perl

@@ -344,26 +344,27 @@ sub do_cmd_deprecated{
             . $_);
 }
 
-sub do_cmd_versionadded{
-    # one parameter:  \versionadded{version}
-    local($_) = @_;
-    my $release = next_argument();
-    return ("\n<span class='versionnote'>New in version $release.</span>\n"
-            . $_);
-}
-
-sub do_cmd_versionchanged{
-    # one parameter:  \versionchanged{version}
-    local($_) = @_;
+sub versionnote{
+    # one or two parameters:  \versionnote[explanation]{version}
+    my $type = @_[0];
+    local $_ = @_[1];
     my $explanation = next_optional_argument();
     my $release = next_argument();
-    my $text = "Changed in version $release.";
+    my $text = "$type in version $release.";
     if ($explanation) {
-        $text = "Changed in version $release:\n$explanation.";
+        $text = "$type in version $release:\n$explanation.";
     }
     return "\n<span class='versionnote'>$text</span>\n" . $_;
 }
 
+sub do_cmd_versionadded{
+    return versionnote('New', @_);
+}
+
+sub do_cmd_versionchanged{
+    return versionnote('Changed', @_);
+}
+
 #
 # These function handle platform dependency tracking.
 #