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/screen.c b/src/screen.c
index 825b7ab..fdb1e0a 100644
--- a/src/screen.c
+++ b/src/screen.c
@@ -3120,8 +3120,13 @@
 		{
 		    if (nrcol)
 		    {
-			sprintf((char *)extra, "%*s ", number_width(wp),
-								*pp_extra);
+			int n, width = number_width(wp) - 2;
+
+			for (n = 0; n < width; n++)
+			    extra[n] = ' ';
+			extra[n] = 0;
+			STRCAT(extra, *pp_extra);
+			STRCAT(extra, " ");
 			*pp_extra = extra;
 		    }
 		    *c_extrap = NUL;
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
diff --git a/src/version.c b/src/version.c
index 6c6550b..a6d1492 100644
--- a/src/version.c
+++ b/src/version.c
@@ -778,6 +778,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1712,
+/**/
     1711,
 /**/
     1710,