patch 8.1.0572: stopping a job does not work properly on OpenBSD

Problem:    Stopping a job does not work properly on OpenBSD.
Solution:   Do not use getpgid() to check the process group of the job
            processs ID, always pass the negative process ID to kill().
            (George Koehler, closes #3656)
diff --git a/src/version.c b/src/version.c
index 049f34b..9311bc5 100644
--- a/src/version.c
+++ b/src/version.c
@@ -793,6 +793,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    572,
+/**/
     571,
 /**/
     570,