patch 8.1.1712: signs in number column cause text to be misaligned

Problem:    Signs in number column cause text to be misaligned.
Solution:   Improve alignment. (Yasuhiro Matsumoto, closes #4694)
diff --git a/src/testdir/test_signs.vim b/src/testdir/test_signs.vim
index 1b9a29d..3d885d6 100644
--- a/src/testdir/test_signs.vim
+++ b/src/testdir/test_signs.vim
@@ -1766,6 +1766,7 @@
   set number
   set signcolumn=number
   sign define sign1 text==>
+  sign define sign2 text=V
   sign place 10 line=1 name=sign1
   redraw!
   call assert_equal("=> 01234", s:ScreenLine(1, 1, 8))
@@ -1846,6 +1847,12 @@
   redraw!
   call assert_equal("=> 01234", s:ScreenLine(1, 1, 8))
   call assert_equal(" 2 abcde", s:ScreenLine(2, 1, 8))
+  " Add sign with multi-byte text
+  set numberwidth=4
+  sign place 40 line=2 name=sign2
+  redraw!
+  call assert_equal(" => 01234", s:ScreenLine(1, 1, 9))
+  call assert_equal(" V abcde", s:ScreenLine(2, 1, 9))
 
   sign unplace * group=*
   sign undefine sign1