make bitcoin include files more modular

src/irc.h

@@ -1,9 +1,13 @@
 // Copyright (c) 2009-2010 Satoshi Nakamoto
 // Distributed under the MIT/X11 software license, see the accompanying
 // file license.txt or http://www.opensource.org/licenses/mit-license.php.
+#ifndef BITCOIN_IRC_H
+#define BITCOIN_IRC_H
 
-bool RecvLine(SOCKET hSocket, string& strLine);
+bool RecvLine(SOCKET hSocket, std::string& strLine);
 void ThreadIRCSeed(void* parg);
 
 extern int nGotIRCAddresses;
 extern bool fGotExternalIP;
+
+#endif