patch 8.1.2418: bufnr('$') is wrong after recycling popup buffer

Problem:    bufnr('$') is wrong after recycling popup buffer.
Solution:   Sort the buffer list by buffer number. (closes #5335)
diff --git a/src/version.c b/src/version.c
index 0956f87..ecdcb9c 100644
--- a/src/version.c
+++ b/src/version.c
@@ -743,6 +743,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    2418,
+/**/
     2417,
 /**/
     2416,