Move swarmHash to its own file.

libdevcore/SwarmHash.h

@@ -0,0 +1,31 @@
+/*
+	This file is part of cpp-ethereum.
+
+	cpp-ethereum is free software: you can redistribute it and/or modify
+	it under the terms of the GNU General Public License as published by
+	the Free Software Foundation, either version 3 of the License, or
+	(at your option) any later version.
+
+	cpp-ethereum is distributed in the hope that it will be useful,
+	but WITHOUT ANY WARRANTY; without even the implied warranty of
+	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+	GNU General Public License for more details.
+
+	You should have received a copy of the GNU General Public License
+	along with cpp-ethereum.  If not, see <http://www.gnu.org/licenses/>.
+*/
+/** @file SwarmHash.h
+ */
+
+#pragma once
+
+#include <libdevcore/FixedHash.h>
+#include <libdevcore/Common.h>
+
+namespace dev
+{
+
+/// Compute the "swarm hash" of @a _data
+h256 swarmHash(bytes const& _data);
+
+}