patch 8.2.1133: Vim9: return type of add() is not specific enough

Problem:    Vim9: return type of add() is not specific enough.
Solution:   Return the type of the first argument. (closes #6395)

src/evalfunc.c

@@ -441,7 +441,7 @@ static funcentry_T global_functions[] =
 {
     {"abs",		1, 1, FEARG_1,	  ret_any,	FLOAT_FUNC(f_abs)},
     {"acos",		1, 1, FEARG_1,	  ret_float,	FLOAT_FUNC(f_acos)},
-    {"add",		2, 2, FEARG_1,	  ret_any,	f_add},
+    {"add",		2, 2, FEARG_1,	  ret_first_arg, f_add},
     {"and",		2, 2, FEARG_1,	  ret_number,	f_and},
     {"append",		2, 2, FEARG_LAST, ret_number,	f_append},
     {"appendbufline",	3, 3, FEARG_LAST, ret_number,	f_appendbufline},

src/testdir/test_vim9_func.vim

@@ -602,6 +602,12 @@ def Test_repeat_return_type()
     res += n
   endfor
   assert_equal(3, res)
+
+  res = 0
+  for n in add([1, 2], 3)
+    res += n
+  endfor
+  assert_equal(6, res)
 enddef
 
 def Test_func_type_part()

src/version.c

@@ -754,6 +754,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1133,
 /**/
     1132,
 /**/