patch 8.2.4825: can only get a list of mappings

Problem:    Can only get a list of mappings.
Solution:   Add the optional {abbr} argument. (Ernie Rael, closes #10277)
            Rename to maplist().  Rename test file.

src/map.c

@@ -2389,10 +2389,10 @@ get_maparg(typval_T *argvars, typval_T *rettv, int exact)
 }
 
 /*
- * "getmappings()" function
+ * "maplist()" function
  */
     void
-f_getmappings(typval_T *argvars UNUSED, typval_T *rettv)
+f_maplist(typval_T *argvars UNUSED, typval_T *rettv)
 {
     dict_T	*d;
     mapblock_T	*mp;
@@ -2402,6 +2402,12 @@ f_getmappings(typval_T *argvars UNUSED, typval_T *rettv)
     int		hash;
     char_u	*lhs;
     const int	flags = REPTERM_FROM_PART | REPTERM_DO_LT;
+    int		abbr = FALSE;
+
+    if (in_vim9script() && check_for_opt_bool_arg(argvars, 0) == FAIL)
+	return;
+    if (argvars[0].v_type != VAR_UNKNOWN)
+	abbr = tv_get_bool(&argvars[0]);
 
     if (rettv_list_alloc(rettv) != OK)
 	return;
@@ -2413,7 +2419,16 @@ f_getmappings(typval_T *argvars UNUSED, typval_T *rettv)
     {
 	for (hash = 0; hash < 256; ++hash)
 	{
-	    if (buffer_local)
+	    if (abbr)
+	    {
+		if (hash > 0)		// there is only one abbr list
+		    break;
+		if (buffer_local)
+		    mp = curbuf->b_first_abbr;
+		else
+		    mp = first_abbr;
+	    }
+	    else if (buffer_local)
 		mp = curbuf->b_maphash[hash];
 	    else
 		mp = maphash[hash];