patch 8.0.0942: using freed memory with ":terminal"

Problem:    Using freed memory with ":terminal" if an autocommand changes
            'shell' when splitting the window. (Marius Gedminas)
Solution:   Make a copy of 'shell'. (closes #1974)

src/version.c

@@ -769,6 +769,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    942,
 /**/
     941,
 /**/