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.h

@@ -13,7 +13,7 @@ static const bool DEFAULT_CHOOSE_DATADIR = false;
 
 class FreespaceChecker;
 
-namespace interface {
+namespace interfaces {
     class Node;
 }
 
@@ -45,7 +45,7 @@ public:
      * @note do NOT call global GetDataDir() before calling this function, this
      * will cause the wrong path to be cached.
      */
-    static bool pickDataDirectory(interface::Node& node);
+    static bool pickDataDirectory(interfaces::Node& node);
 
     /**
      * Determine default data directory for operating system.