patch 8.1.0493: argv() and argc() only work on the current argument list

Problem:    argv() and argc() only work on the current argument list.
Solution:   Add a window ID argument. (Yegappan Lakshmanan, closes #832)
diff --git a/src/testdir/test_arglist.vim b/src/testdir/test_arglist.vim
index 057cb0d..b896c3d 100644
--- a/src/testdir/test_arglist.vim
+++ b/src/testdir/test_arglist.vim
@@ -278,13 +278,53 @@
   call assert_equal(0, arglistid())
 endfunc
 
-" Test for argv()
+" Tests for argv() and argc()
 func Test_argv()
   call Reset_arglist()
   call assert_equal([], argv())
   call assert_equal("", argv(2))
+  call assert_equal(0, argc())
   argadd a b c d
+  call assert_equal(4, argc())
   call assert_equal('c', argv(2))
+
+  let w1_id = win_getid()
+  split
+  let w2_id = win_getid()
+  arglocal
+  args e f g
+  tabnew
+  let w3_id = win_getid()
+  split
+  let w4_id = win_getid()
+  argglobal
+  tabfirst
+  call assert_equal(4, argc(w1_id))
+  call assert_equal('b', argv(1, w1_id))
+  call assert_equal(['a', 'b', 'c', 'd'], argv(-1, w1_id))
+
+  call assert_equal(3, argc(w2_id))
+  call assert_equal('f', argv(1, w2_id))
+  call assert_equal(['e', 'f', 'g'], argv(-1, w2_id))
+
+  call assert_equal(3, argc(w3_id))
+  call assert_equal('e', argv(0, w3_id))
+  call assert_equal(['e', 'f', 'g'], argv(-1, w3_id))
+
+  call assert_equal(4, argc(w4_id))
+  call assert_equal('c', argv(2, w4_id))
+  call assert_equal(['a', 'b', 'c', 'd'], argv(-1, w4_id))
+
+  call assert_equal(4, argc(-1))
+  call assert_equal(3, argc())
+  call assert_equal('d', argv(3, -1))
+  call assert_equal(['a', 'b', 'c', 'd'], argv(-1, -1))
+  tabonly | only | enew!
+  " Negative test cases
+  call assert_equal(-1, argc(100))
+  call assert_equal('', argv(1, 100))
+  call assert_equal([], argv(-1, 100))
+  call assert_equal('', argv(10, -1))
 endfunc
 
 " Test for the :argedit command