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/intro.cpp

@@ -12,7 +12,7 @@
 
 #include <qt/guiutil.h>
 
-#include <interface/node.h>
+#include <interfaces/node.h>
 #include <util.h>
 
 #include <QFileDialog>
@@ -187,7 +187,7 @@ QString Intro::getDefaultDataDirectory()
     return GUIUtil::boostPathToQString(GetDefaultDataDir());
 }
 
-bool Intro::pickDataDirectory(interface::Node& node)
+bool Intro::pickDataDirectory(interfaces::Node& node)
 {
     QSettings settings;
     /* If data directory provided on command line, no need to look at settings