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/optionsmodel.cpp

@@ -11,7 +11,7 @@
 #include <qt/bitcoinunits.h>
 #include <qt/guiutil.h>
 
-#include <interface/node.h>
+#include <interfaces/node.h>
 #include <validation.h> // For DEFAULT_SCRIPTCHECK_THREADS
 #include <net.h>
 #include <netbase.h>
@@ -24,7 +24,7 @@
 
 const char *DEFAULT_GUI_PROXY_HOST = "127.0.0.1";
 
-OptionsModel::OptionsModel(interface::Node& node, QObject *parent, bool resetSettings) :
+OptionsModel::OptionsModel(interfaces::Node& node, QObject *parent, bool resetSettings) :
     QAbstractListModel(parent), m_node(node)
 {
     Init(resetSettings);