patch 8.2.0916: mapping with partly modifyOtherKeys code does not work

Problem:    Mapping with partly modifyOtherKeys code does not work.
Solution:   If there is no mapping with a separate modifier include the
            modifier in the key and then try mapping again. (closes #6200)
diff --git a/src/proto/getchar.pro b/src/proto/getchar.pro
index 57d78b5..bf131a5 100644
--- a/src/proto/getchar.pro
+++ b/src/proto/getchar.pro
@@ -37,7 +37,7 @@
 void close_all_scripts(void);
 int using_script(void);
 void before_blocking(void);
-int merge_modifyOtherKeys(int c_arg);
+int merge_modifyOtherKeys(int c_arg, int *modifiers);
 int vgetc(void);
 int safe_vgetc(void);
 int plain_vgetc(void);