patch 8.2.0258: modifyOtherKeys cannot be temporarily disabled

Problem:    ModifyOtherKeys cannot be temporarily disabled.
Solution:   Add echoraw() with an example for modifyOtherKeys.
diff --git a/src/evalfunc.c b/src/evalfunc.c
index a0f2994..3e1a462 100644
--- a/src/evalfunc.c
+++ b/src/evalfunc.c
@@ -60,6 +60,7 @@
 #endif
 static void f_deepcopy(typval_T *argvars, typval_T *rettv);
 static void f_did_filetype(typval_T *argvars, typval_T *rettv);
+static void f_echoraw(typval_T *argvars, typval_T *rettv);
 static void f_empty(typval_T *argvars, typval_T *rettv);
 static void f_environ(typval_T *argvars, typval_T *rettv);
 static void f_escape(typval_T *argvars, typval_T *rettv);
@@ -394,6 +395,7 @@
     {"did_filetype",	0, 0, 0,	  &t_number,	f_did_filetype},
     {"diff_filler",	1, 1, FEARG_1,	  &t_number,	f_diff_filler},
     {"diff_hlID",	2, 2, FEARG_1,	  &t_number,	f_diff_hlID},
+    {"echoraw",		1, 1, FEARG_1,	  &t_number,	f_echoraw},
     {"empty",		1, 1, FEARG_1,	  &t_number,	f_empty},
     {"environ",		0, 0, 0,	  &t_dict_string, f_environ},
     {"escape",		2, 2, FEARG_1,	  &t_string,	f_escape},
@@ -1814,6 +1816,21 @@
 }
 
 /*
+ * "echoraw({expr})" function
+ */
+    static void
+f_echoraw(typval_T *argvars, typval_T *rettv UNUSED)
+{
+    char_u *str = tv_get_string_chk(&argvars[0]);
+
+    if (str != NULL && *str != NUL)
+    {
+	out_str(str);
+	out_flush();
+    }
+}
+
+/*
  * "empty({expr})" function
  */
     static void