patch 8.1.1899: sign_place() does not work as documented

Problem:    sign_place() does not work as documented.
Solution:   Make accept line numbers like line(). (Yegappan Lakshmanan,
            closes #4848)
diff --git a/src/testdir/test_signs.vim b/src/testdir/test_signs.vim
index 3d885d6..06b2571 100644
--- a/src/testdir/test_signs.vim
+++ b/src/testdir/test_signs.vim
@@ -457,11 +457,11 @@
   call assert_fails('call sign_place(5, "", "sign1", [], {"lnum" : 10})',
 	      \ 'E158:')
   call assert_fails('call sign_place(21, "", "sign1", "Xsign",
-	      \ {"lnum" : -1})', 'E885:')
+	      \ {"lnum" : -1})', 'E474:')
   call assert_fails('call sign_place(22, "", "sign1", "Xsign",
-	      \ {"lnum" : 0})', 'E885:')
+	      \ {"lnum" : 0})', 'E474:')
   call assert_fails('call sign_place(22, "", "sign1", "Xsign",
-	      \ {"lnum" : []})', 'E745:')
+	      \ {"lnum" : []})', 'E474:')
   call assert_equal(-1, sign_place(1, "*", "sign1", "Xsign", {"lnum" : 10}))
 
   " Tests for sign_getplaced()
@@ -517,6 +517,16 @@
   call assert_fails('call sign_undefine("none")', 'E155:')
   call assert_fails('call sign_undefine({})', 'E731:')
 
+  " Test for using '.' as the line number for sign_place()
+  call sign_define("sign1", attr)
+  call cursor(22, 1)
+  call assert_equal(15, sign_place(15, '', 'sign1', 'Xsign',
+	      \ {'lnum' : '.'}))
+  call assert_equal([{'bufnr' : bufnr(''), 'signs' :
+	      \ [{'id' : 15, 'group' : '', 'lnum' : 22, 'name' : 'sign1',
+	      \ 'priority' : 10}]}],
+	      \ sign_getplaced('%', {'lnum' : 22}))
+
   call delete("Xsign")
   call sign_unplace('*')
   call sign_undefine()
@@ -1928,6 +1938,14 @@
   call assert_equal([{'id' : 5, 'name' : 'sign1', 'lnum' : 11,
 	      \ 'group' : '', 'priority' : 10}], s[0].signs)
 
+  " Place a sign using '.' as the line number
+  call cursor(23, 1)
+  call assert_equal([7], sign_placelist([
+	      \ {'id' : 7, 'name' : 'sign1', 'buffer' : '%', 'lnum' : '.'}]))
+  let s = sign_getplaced('%', {'lnum' : '.'})
+  call assert_equal([{'id' : 7, 'name' : 'sign1', 'lnum' : 23,
+	      \ 'group' : '', 'priority' : 10}], s[0].signs)
+
   " Place sign without a sign name
   call assert_equal([-1], sign_placelist([{'id' : 10, 'buffer' : 'Xsign',
 	      \ 'lnum' : 12, 'group' : ''}]))