Added MSVC10 solution and project files for Windows

These include configurations for both Win32 and x64 platforms. All project
settings have been normalised in property sheets (the ".props" files under
builds/msvc/properties) to simplify maintenance. Build artefacts are all
generated in platform-specific subfolders of bin, lib and obj directories.

Also enables the use of precompiled headers with MSVC10.

This significantly reduces the time required to compile libzmq with Visual
Studio on Windows. It should have no impact on other platforms.

Signed-off-by: Stuart Webster <sw_webster@hotmail.com>

src/precompiled.hpp

@@ -0,0 +1,47 @@
+/*
+    Copyright (c) 2011 250bpm s.r.o.
+    Copyright (c) 2011 Other contributors as noted in the AUTHORS file
+
+    This file is part of 0MQ.
+
+    0MQ is free software; you can redistribute it and/or modify it under
+    the terms of the GNU Lesser General Public License as published by
+    the Free Software Foundation; either version 3 of the License, or
+    (at your option) any later version.
+
+    0MQ 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 Lesser General Public License for more details.
+
+    You should have received a copy of the GNU Lesser General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __ZMQ_PRECOMPILED_HPP_INCLUDED__
+#define __ZMQ_PRECOMPILED_HPP_INCLUDED__
+
+#ifdef _MSC_VER
+
+// Windows headers
+#include "platform.hpp"
+#include "windows.hpp"
+#include <fcntl.h>
+#include <intrin.h>
+#include <io.h>
+#include <rpc.h>
+#include <sys/stat.h>
+
+// standard C++ headers
+#include <algorithm>
+#include <map>
+#include <set>
+#include <string>
+#include <vector>
+
+// 0MQ definitions and exported functions
+#include "../include/zmq.h"
+
+#endif // _MSC_VER
+
+#endif