patch 8.0.1593: :qall never exits with an active terminal window

Problem:    :qall never exits with an active terminal window.
Solution:   Add a way to kill a job in a terminal window.
diff --git a/src/evalfunc.c b/src/evalfunc.c
index aa0ec60..1620efe 100644
--- a/src/evalfunc.c
+++ b/src/evalfunc.c
@@ -867,6 +867,7 @@
     {"term_list",	0, 0, f_term_list},
     {"term_scrape",	2, 2, f_term_scrape},
     {"term_sendkeys",	2, 2, f_term_sendkeys},
+    {"term_setkill",	2, 2, f_term_setkill},
     {"term_setrestore",	2, 2, f_term_setrestore},
     {"term_start",	1, 2, f_term_start},
     {"term_wait",	1, 2, f_term_wait},