Add the conceal patch from Vince Negri.

runtime/doc/todo.txt

@@ -1082,6 +1082,10 @@ restored. (Luc St-Louis)
 
 
 Vim 7.3:
+- Included conceal patch.
+    remove w:ownsyntax, automatically set w:current_syntax to the value of
+    b:current_syntax after loading a syntax file.
+    :ownsyntax only sets w:current_syntax.
 - using NSIS 2.46: install on Windows 7 works, but no "Edit with Vim" menu.
    Use register_shell_extension()? (George Reilly, 2010 May 26)
    Ron's version: http://dev.ronware.org/p/vim/finfo?name=gvim.nsi
@@ -1108,10 +1112,6 @@ Vim 7.3:
 - Create a helphelp.txt file, move instructions there to write help files from
   various.txt and list by Tony.
 Patches to include:
-- Include conceal patch?
-  http://vince.negri.googlepages.com/
-  http://vim.wikia.com/wiki/Patch_to_conceal_parts_of_lines
-  http://sites.google.com/site/vincenegri/conceal-ownsyntax.diff?attredirects=0
 - Patch for Lisp support with ECL (Mikael Jansson, 2008 Oct 25)
 - Minor patches from Dominique Pelle, 2010 May 15
 - Gvimext patch to support wide file names. (Szabolcs Horvat 2008 Sep 10)