patch 8.1.1159: MS-Windows: with a silent (un)install $VIM/_vimrc is removed

Problem:    MS-Windows: with a silent (un)install $VIM/_vimrc is removed.
Solution:   Don't delete _vimrc in silent mode. (Ken Takata, closes #4242)
diff --git a/nsis/gvim.nsi b/nsis/gvim.nsi
index 8336093..2e990b8 100644
--- a/nsis/gvim.nsi
+++ b/nsis/gvim.nsi
@@ -1096,7 +1096,9 @@
 	Call un.GetParent
 	Pop $0
 
-	Delete $0\_vimrc
+	${IfNot} ${Silent}
+	  Delete $0\_vimrc
+	${Endif}
 	RMDir $0
 SectionEnd
 
diff --git a/src/version.c b/src/version.c
index 7e5d406..46341ee 100644
--- a/src/version.c
+++ b/src/version.c
@@ -772,6 +772,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1159,
+/**/
     1158,
 /**/
     1157,