Description: Make sure to use qualified lookups.
http://bugs.debian.org/667430
https://bugs.gentoo.org/show_bug.cgi?id=414133

Author: Cyril Brulebois <kibi@debian.org>
--- a/include/zthread/Guard.h
+++ b/include/zthread/Guard.h
@@ -428,7 +428,7 @@
   template <class U, class V>
   Guard(Guard<U, V>& g) : LockHolder<LockType>(g) {
 
-    LockingPolicy::shareScope(*this, extract(g));
+    LockingPolicy::shareScope(*this, this->extract(g));
     
   }
 
@@ -458,7 +458,7 @@
   template <class U, class V>
   Guard(Guard<U, V>& g, LockType& lock) : LockHolder<LockType>(lock) {
 
-    LockingPolicy::transferScope(*this, extract(g));
+    LockingPolicy::transferScope(*this, this->extract(g));
 
   }