patch 8.1.0619: :echomsg and :echoerr do not handle List and Dict

Problem:    :echomsg and :echoerr do not handle List and Dict like :echo does.
            (Daniel Hahler)
Solution:   Be more tolerant about the expression result type.
diff --git a/src/evalfunc.c b/src/evalfunc.c
index cbe2a4e..bd2acef 100644
--- a/src/evalfunc.c
+++ b/src/evalfunc.c
@@ -396,7 +396,6 @@
 #endif
 static void f_strgetchar(typval_T *argvars, typval_T *rettv);
 static void f_stridx(typval_T *argvars, typval_T *rettv);
-static void f_string(typval_T *argvars, typval_T *rettv);
 static void f_strlen(typval_T *argvars, typval_T *rettv);
 static void f_strcharpart(typval_T *argvars, typval_T *rettv);
 static void f_strpart(typval_T *argvars, typval_T *rettv);
@@ -12475,7 +12474,7 @@
 /*
  * "string()" function
  */
-    static void
+    void
 f_string(typval_T *argvars, typval_T *rettv)
 {
     char_u	*tofree;