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-

doc/developer-notes.md

@@ -626,7 +626,7 @@ GUI
     holds: try to not directly access core data structures from Views.
 
 - Avoid adding slow or blocking code in the GUI thread. In particular do not
-  add new `interface::Node` and `interface::Wallet` method calls, even if they
+  add new `interfaces::Node` and `interfaces::Wallet` method calls, even if they
   may be fast now, in case they are changed to lock or communicate across
   processes in the future.