patch 8.1.0230: directly checking 'buftype' value

Problem:    Directly checking 'buftype' value.
Solution:   Add the bt_normal() function. (Yegappan Lakshmanan)
diff --git a/src/version.c b/src/version.c
index 5f7d908..e0af020 100644
--- a/src/version.c
+++ b/src/version.c
@@ -795,6 +795,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    230,
+/**/
     229,
 /**/
     228,