patch 8.2.2873: not enough tests for writing buffers

Problem:    Not enough tests for writing buffers.
Solution:   Add a few more tests. (Yegappan Lakshmanan, closes #8229)
diff --git a/src/version.c b/src/version.c
index af40462..7fd4338 100644
--- a/src/version.c
+++ b/src/version.c
@@ -751,6 +751,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    2873,
+/**/
     2872,
 /**/
     2871,