patch 8.0.0884: can't specify the wait time for term_wait()

Problem:    Can't specify the wait time for term_wait().
Solution:   Add an otional second argument.

runtime/doc/eval.txt

@@ -2381,7 +2381,7 @@ term_list()			List	get the list of terminal buffers
 term_scrape({buf}, {row})	List	get row of a terminal screen
 term_sendkeys({buf}, {keys})	none	send keystrokes to a terminal
 term_start({cmd}, {options})	Job	open a terminal window and run a job
-term_wait({buf})		Number  wait for screen to be updated
+term_wait({buf} [, {time}])	Number  wait for screen to be updated
 test_alloc_fail({id}, {countdown}, {repeat})
 				none	make memory allocation fail
 test_autochdir()		none	enable 'autochdir' during startup
@@ -8041,9 +8041,11 @@ term_start({cmd}, {options})				*term_start()*
 				 the command name.
 		{only available when compiled with the |+terminal| feature}
 
-term_wait({buf})						*term_wait()*
+term_wait({buf} [, {time}])					*term_wait()*
 		Wait for pending updates of {buf} to be handled.
 		{buf} is used as with |term_getsize()|.
+		{time} is how long to wait for updates to arrive in msec.  If
+		not set then 10 msec will be used.
 		{only available when compiled with the |+terminal| feature}
 
 test_alloc_fail({id}, {countdown}, {repeat})		*test_alloc_fail()*

src/evalfunc.c

@@ -843,7 +843,7 @@ static struct fst
     {"term_scrape",	2, 2, f_term_scrape},
     {"term_sendkeys",	2, 2, f_term_sendkeys},
     {"term_start",	1, 2, f_term_start},
-    {"term_wait",	1, 1, f_term_wait},
+    {"term_wait",	1, 2, f_term_wait},
 #endif
     {"test_alloc_fail",	3, 3, f_test_alloc_fail},
     {"test_autochdir",	0, 0, f_test_autochdir},

src/terminal.c

@@ -36,7 +36,6 @@
  * that buffer, attributes come from the scrollback buffer tl_scrollback.
  *
  * TODO:
- * - Add argument to term_wait() for waiting time.
  * - For the scrollback buffer store lines in the buffer, only attributes in
  *   tl_scrollback.
  * - When the job ends:
@@ -2248,12 +2247,15 @@ f_term_wait(typval_T *argvars, typval_T *rettv UNUSED)
     }
     else
     {
+	long wait = 10L;
+
 	mch_check_messages();
 	parse_queued_messages();
 
-	/* Wait for 10 msec for any channel I/O. */
-	/* TODO: use delay from optional argument */
-	ui_delay(10L, TRUE);
+	/* Wait for some time for any channel I/O. */
+	if (argvars[1].v_type != VAR_UNKNOWN)
+	    wait = get_tv_number(&argvars[1]);
+	ui_delay(wait, TRUE);
 	mch_check_messages();
 
 	/* Flushing messages on channels is hopefully sufficient.

src/version.c

@@ -769,6 +769,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    884,
 /**/
     883,
 /**/