patch 8.2.0295: highlighting for :s wrong when using different separator

Problem:    Highlighting for :s wrong when using different separator.
Solution:   Use separat argument for search direction and separator. (Rob
            Pilling, closes #5665)
diff --git a/src/gui.c b/src/gui.c
index f1c36f4..3f2a84c 100644
--- a/src/gui.c
+++ b/src/gui.c
@@ -5374,7 +5374,7 @@
 	i = msg_scroll;
 	if (down)
 	{
-	    (void)do_search(NULL, '/', ga.ga_data, 1L, searchflags, NULL);
+	    (void)do_search(NULL, '/', '/', ga.ga_data, 1L, searchflags, NULL);
 	}
 	else
 	{
@@ -5382,7 +5382,7 @@
 	    // direction
 	    p = vim_strsave_escaped(ga.ga_data, (char_u *)"?");
 	    if (p != NULL)
-	        (void)do_search(NULL, '?', p, 1L, searchflags, NULL);
+	        (void)do_search(NULL, '?', '?', p, 1L, searchflags, NULL);
 	    vim_free(p);
 	}