patch 8.0.0912: cannot run a job in a hidden terminal

Problem:    Cannot run a job in a hidden terminal.
Solution:   Add option "hidden" and ++hidden.
diff --git a/src/channel.c b/src/channel.c
index 9476276..22d9083 100644
--- a/src/channel.c
+++ b/src/channel.c
@@ -4462,6 +4462,13 @@
 		opt->jo_set |= JO2_CURWIN;
 		opt->jo_curwin = get_tv_number(item);
 	    }
+	    else if (STRCMP(hi->hi_key, "hidden") == 0)
+	    {
+		if (!(supported2 & JO2_HIDDEN))
+		    break;
+		opt->jo_set |= JO2_HIDDEN;
+		opt->jo_hidden = get_tv_number(item);
+	    }
 #endif
 	    else if (STRCMP(hi->hi_key, "env") == 0)
 	    {