fix expensive move code path

IkiWiki/Plugin/attachment.pm

@@ -72,6 +72,9 @@ sub formbuilder (@) { #{{{
 			}
 		}
 
+		# Needed for fast_file_copy.
+		require IkiWiki::Render;
+
 		# Move the attachment into place.
 		# Try to use a fast rename; fall back to copying.
 		IkiWiki::prep_writefile($filename, $config{srcdir});

IkiWiki/Render.pm

@@ -180,7 +180,7 @@ sub scan ($) { #{{{
 	}
 } #}}}
 
-sub fast_file_copy ($$$$$) { #{{{
+sub fast_file_copy (@) { #{{{
 	my $srcfile=shift;
 	my $destfile=shift;
 	my $srcfd=shift;