patch 8.1.2145: cannot map <C-H> when modifyOtherKeys is enabled

Problem:    Cannot map <C-H> when modifyOtherKeys is enabled.
Solution:   Add the <C-H> mapping twice, both with modifier and as 0x08.  Use
            only the first one when modifyOtherKeys has been detected.
diff --git a/src/proto/misc2.pro b/src/proto/misc2.pro
index bcdcd31..a52b462 100644
--- a/src/proto/misc2.pro
+++ b/src/proto/misc2.pro
@@ -67,10 +67,10 @@
 int simplify_key(int key, int *modifiers);
 int handle_x_keys(int key);
 char_u *get_special_key_name(int c, int modifiers);
-int trans_special(char_u **srcp, char_u *dst, int keycode, int in_string);
+int trans_special(char_u **srcp, char_u *dst, int keycode, int in_string, int simplify, int *did_simplify);
 int special_to_buf(int key, int modifiers, int keycode, char_u *dst);
-int find_special_key(char_u **srcp, int *modp, int keycode, int keep_x_key, int in_string);
-int extract_modifiers(int key, int *modp);
+int find_special_key(char_u **srcp, int *modp, int keycode, int keep_x_key, int in_string, int simplify, int *did_simplify);
+int extract_modifiers(int key, int *modp, int simplify, int *did_simplify);
 int find_special_key_in_table(int c);
 int get_special_key_code(char_u *name);
 char_u *get_key_name(int i);