patch 9.0.1210: compiler complains about declaration after label

Problem:    Compiler complains about declaration after label.
Solution:   Move declaration to beginning of block (John Marriott)
diff --git a/src/os_mswin.c b/src/os_mswin.c
index 58d8fbe..5360fa9 100644
--- a/src/os_mswin.c
+++ b/src/os_mswin.c
@@ -1389,6 +1389,7 @@
     DEVMODEW		*mem;
     DEVNAMES		*devname;
     int			i;
+    DWORD		err;
 
     bUserAbort = &(psettings->user_abort);
     CLEAR_FIELD(prt_dlg);
@@ -1571,8 +1572,7 @@
     return TRUE;
 
 init_fail_dlg:
-    DWORD err = CommDlgExtendedError();
-
+    err = CommDlgExtendedError();
     if (err)
     {
 	char_u *buf;