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/walletmodeltransaction.h

@@ -13,7 +13,7 @@
 
 class SendCoinsRecipient;
 
-namespace interface {
+namespace interfaces {
 class Node;
 class PendingWalletTx;
 }
@@ -26,7 +26,7 @@ public:
 
     QList<SendCoinsRecipient> getRecipients() const;
 
-    std::unique_ptr<interface::PendingWalletTx>& getWtx();
+    std::unique_ptr<interfaces::PendingWalletTx>& getWtx();
     unsigned int getTransactionSize();
 
     void setTransactionFee(const CAmount& newFee);
@@ -38,7 +38,7 @@ public:
 
 private:
     QList<SendCoinsRecipient> recipients;
-    std::unique_ptr<interface::PendingWalletTx> wtx;
+    std::unique_ptr<interfaces::PendingWalletTx> wtx;
     CAmount fee;
 };