Deadlock fix.

libethcore/Ethash.cpp

@@ -255,6 +255,7 @@ public:
 	EthashCLHook(EthashCLHook const&) = delete;
 
 	void abort()
+	{
 		{
 			UniqueGuard l(x_all);
 			if (m_aborted)
@@ -262,6 +263,7 @@ public:
 //		cdebug << "Attempting to abort";
 
 			m_abort = true;
+		}
 		// m_abort is true so now searched()/found() will return true to abort the search.
 		// we hang around on this thread waiting for them to point out that they have aborted since
 		// otherwise we may end up deleting this object prior to searched()/found() being called.