patch 8.1.1229: warning for posix_openpt() not declared

Problem:    Warning for posix_openpt() not declared. (Tony Mechelynck)
Solution:   Add declaration.
diff --git a/src/version.c b/src/version.c
index 7bf4907..675c82f 100644
--- a/src/version.c
+++ b/src/version.c
@@ -768,6 +768,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1229,
+/**/
     1228,
 /**/
     1227,