functions.pl: add missing sub routine for wireguard.cgi

wireguard.cgi calls errorbox and opensection/closesection,
but they are missing from header.pl. ipfire had functons.pl
removed and moved subroutines to header.pl and added errorbox
in header.pl. to keep the change minimum so not affect other
features, add errorbox and opensection/closesection in functions.pl

Signed-off-by: Vincent Li <vincent.mc.li@gmail.com>

html/html/themes/ipfire/include/functions.pl

@@ -265,3 +265,41 @@ sub openbox {
 sub closebox {
 	print "</div>";
 }
+
+sub errorbox($) {
+        my @errors = grep { $_ ne "" } @_;
+
+        # Do nothing if there are no errors
+        return unless (@errors);
+
+        # Open a new box
+        &openbox('100%', 'left', "Oops something went wrong");
+
+        # Print all error messages
+        print "<ul>\n";
+        foreach my $error (@errors) {
+                print "<li>$error</li>\n";
+        }
+        print "</ul>\n";
+
+        # Close the box again
+        &closebox();
+}
+
+# Sections
+
+sub opensection($) {
+        my $title = shift;
+
+        # Open the section
+        print "<section class=\"section\">";
+
+        # Show the title if set
+        if ($title) {
+                print " <h2 class=\"title\">${title}</h2>\n";
+        }
+}
+
+sub closesection() {
+        print "</section>";
+}