patch 8.0.0849: crash when job exit callback wipes the terminal

Problem:    Crash when job exit callback wipes the terminal.
Solution:   Check for b_term to be NULL.  (Yasuhiro Matsumoto, closes #1922)
            Implement options for term_start() to be able to test.
            Make term_wait() more reliable.
diff --git a/src/version.c b/src/version.c
index ae8d0b7..8a02918 100644
--- a/src/version.c
+++ b/src/version.c
@@ -770,6 +770,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    849,
+/**/
     848,
 /**/
     847,