patch 8.2.0839: dropping modifier when putting a character back in typeahead

Problem:    Dropping modifier when putting a character back in typeahead.
Solution:   Add modifier to ins_char_typebuf(). (closes #6158)
diff --git a/src/proto/getchar.pro b/src/proto/getchar.pro
index 9ff6620..57d78b5 100644
--- a/src/proto/getchar.pro
+++ b/src/proto/getchar.pro
@@ -25,7 +25,7 @@
 void stop_redo_ins(void);
 int noremap_keys(void);
 int ins_typebuf(char_u *str, int noremap, int offset, int nottyped, int silent);
-void ins_char_typebuf(int c);
+void ins_char_typebuf(int c, int modifier);
 int typebuf_changed(int tb_change_cnt);
 int typebuf_typed(void);
 int typebuf_maplen(void);