Add the conceal patch from Vince Negri.
diff --git a/src/proto/screen.pro b/src/proto/screen.pro
index c534a1f..937e4ed 100644
--- a/src/proto/screen.pro
+++ b/src/proto/screen.pro
@@ -46,5 +46,6 @@
 int redrawing __ARGS((void));
 int messaging __ARGS((void));
 void showruler __ARGS((int always));
+void update_single_line __ARGS((win_T *buf, linenr_T lnum));
 int number_width __ARGS((win_T *wp));
 /* vim: set ft=c : */