patch 8.0.0255: setpos() does not use the buffer argument for all marks

Problem:    When calling setpos() with a buffer argument it often is ignored.
            (Matthew Malcomson)
Solution:   Make the buffer argument work for all marks local to a buffer.
            (neovim #5713)  Add more tests.
diff --git a/src/version.c b/src/version.c
index e66e1b9..4d73ae6 100644
--- a/src/version.c
+++ b/src/version.c
@@ -765,6 +765,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    255,
+/**/
     254,
 /**/
     253,