patch 8.1.2350: other text for CTRL-V in Insert mode with modifyOtherKeys

Problem:    Other text for CTRL-V in Insert mode with modifyOtherKeys.
Solution:   Convert the Escape sequence back to key as if modifyOtherKeys is
            not set, and use CTRL-SHIFT-V to get the Escape sequence itself.
            (closes #5254)
diff --git a/src/proto/edit.pro b/src/proto/edit.pro
index bc69b41..49b9f4c 100644
--- a/src/proto/edit.pro
+++ b/src/proto/edit.pro
@@ -2,6 +2,7 @@
 int edit(int cmdchar, int startln, long count);
 int ins_need_undo_get(void);
 void ins_redraw(int ready);
+int decodeModifyOtherKeys(int c);
 void edit_putchar(int c, int highlight);
 char_u *prompt_text(void);
 int prompt_curpos_editable(void);
diff --git a/src/proto/getchar.pro b/src/proto/getchar.pro
index cfb3ab4..0e24bd3 100644
--- a/src/proto/getchar.pro
+++ b/src/proto/getchar.pro
@@ -37,6 +37,7 @@
 void close_all_scripts(void);
 int using_script(void);
 void before_blocking(void);
+int merge_modifyOtherKeys(int c_arg);
 int vgetc(void);
 int safe_vgetc(void);
 int plain_vgetc(void);
diff --git a/src/proto/term.pro b/src/proto/term.pro
index 5af1996..8f1d33c 100644
--- a/src/proto/term.pro
+++ b/src/proto/term.pro
@@ -65,6 +65,7 @@
 void del_termcode(char_u *name);
 void set_mouse_topline(win_T *wp);
 int is_mouse_topline(win_T *wp);
+int decode_modifiers(int n);
 int check_termcode(int max_offset, char_u *buf, int bufsize, int *buflen);
 void term_get_fg_color(char_u *r, char_u *g, char_u *b);
 void term_get_bg_color(char_u *r, char_u *g, char_u *b);