Replace boost::reverse_lock with our own.

src/reverselock.h

@@ -0,0 +1,31 @@
+// Copyright (c) 2015 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_REVERSELOCK_H
+#define BITCOIN_REVERSELOCK_H
+
+/**
+ * An RAII-style reverse lock. Unlocks on construction and locks on destruction.
+ */
+template<typename Lock>
+class reverse_lock
+{
+public:
+
+    explicit reverse_lock(Lock& lock) : lock(lock) {
+        lock.unlock();
+    }
+
+    ~reverse_lock() {
+        lock.lock();
+    }
+
+private:
+    reverse_lock(reverse_lock const&);
+    reverse_lock& operator=(reverse_lock const&);
+
+    Lock& lock;
+};
+
+#endif // BITCOIN_REVERSELOCK_H