scripted-diff: Avoid interface keyword to fix windows gitian build

Rename `interface` to `interfaces`

Build failure reported by Chun Kuan Lee <ken2812221@gmail.com>
https://github.com/bitcoin/bitcoin/pull/10244#issuecomment-379434756

-BEGIN VERIFY SCRIPT-

git mv src/interface src/interfaces
ren() { git grep -l "$1" | xargs sed -i "s,$1,$2,g"; }
ren interface/            interfaces/
ren interface::           interfaces::
ren BITCOIN_INTERFACE_    BITCOIN_INTERFACES_
ren "namespace interface" "namespace interfaces"

-END VERIFY SCRIPT-

src/qt/utilitydialog.cpp

@@ -19,7 +19,7 @@
 
 #include <clientversion.h>
 #include <init.h>
-#include <interface/node.h>
+#include <interfaces/node.h>
 #include <util.h>
 
 #include <stdio.h>
@@ -32,7 +32,7 @@
 #include <QVBoxLayout>
 
 /** "Help message" or "About" dialog box */
-HelpMessageDialog::HelpMessageDialog(interface::Node& node, QWidget *parent, bool about) :
+HelpMessageDialog::HelpMessageDialog(interfaces::Node& node, QWidget *parent, bool about) :
     QDialog(parent),
     ui(new Ui::HelpMessageDialog)
 {