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/structs.h b/src/structs.h
index 9e2bfa6..767b0f4 100644
--- a/src/structs.h
+++ b/src/structs.h
@@ -1692,7 +1692,8 @@
 #define JO2_TERM_COLS	    0x0080	/* "term_cols" */
 #define JO2_VERTICAL	    0x0100	/* "vertical" */
 #define JO2_CURWIN	    0x0200	/* "curwin" */
-#define JO2_ALL		    0x03FF
+#define JO2_HIDDEN	    0x0400	/* "hidden" */
+#define JO2_ALL		    0x07FF
 
 #define JO_MODE_ALL	(JO_MODE + JO_IN_MODE + JO_OUT_MODE + JO_ERR_MODE)
 #define JO_CB_ALL \
@@ -1754,6 +1755,7 @@
     int		jo_term_cols;
     int		jo_vertical;
     int		jo_curwin;
+    int		jo_hidden;
     char_u	*jo_term_name;
     int		jo_term_finish;
 #endif