Import libcurl for Windows

This was SVN commit r8924.

source/lib/external_libraries/curl.h

@@ -0,0 +1,48 @@
+/* Copyright (c) 2011 Wildfire Games
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining
+ * a copy of this software and associated documentation files (the
+ * "Software"), to deal in the Software without restriction, including
+ * without limitation the rights to use, copy, modify, merge, publish,
+ * distribute, sublicense, and/or sell copies of the Software, and to
+ * permit persons to whom the Software is furnished to do so, subject to
+ * the following conditions:
+ * 
+ * The above copyright notice and this permission notice shall be included
+ * in all copies or substantial portions of the Software.
+ * 
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+ * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+ * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
+ * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
+ * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
+ * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+/*
+ * bring in libcurl header, with compatibility fixes
+ */
+
+#ifndef INCLUDED_CURL
+#define INCLUDED_CURL
+
+// curl.h wants to include winsock2.h which causes conflicts.
+// provide some required definitions from winsock.h, then pretend
+// we already included winsock.h
+
+typedef uintptr_t SOCKET;
+
+struct sockaddr
+{
+	unsigned short sa_family;
+	char sa_data[14];
+};
+
+struct fd_set;
+
+#define _WINSOCKAPI_	// winsock.h include guard
+
+#include <curl/curl.h>
+
+#endif	// #ifndef INCLUDED_CURL