Partial backport of 06b5828dc4649bc23197712fe17b2d4e8d0adbbe

Fix QTerminal keycode for Shift-F3 (previous in search)
--- a/CRT.c
+++ b/CRT.c
@@ -698,6 +698,7 @@
       define_key("\033OQ", KEY_F(2));
       define_key("\033OR", KEY_F(3));
       define_key("\033OS", KEY_F(4));
+      define_key("\033O2R", KEY_F(15));
       define_key("\033[11~", KEY_F(1));
       define_key("\033[12~", KEY_F(2));
       define_key("\033[13~", KEY_F(3));