VC2010 compile fixes

src/main.h

@@ -11,6 +11,10 @@
 #include "script.h"
 #include "db.h"
 
+#ifdef WIN32
+#include <io.h> /* for _commit */
+#endif
+
 #include <list>
 
 class CBlock;
@@ -161,7 +165,7 @@ public:
     std::string ToString() const
     {
         if (IsNull())
-            return strprintf("null");
+            return "null";
         else
             return strprintf("(nFile=%d, nBlockPos=%d, nTxPos=%d)", nFile, nBlockPos, nTxPos);
     }
@@ -288,7 +292,7 @@ public:
     std::string ToString() const
     {
         std::string str;
-        str += strprintf("CTxIn(");
+        str += "CTxIn(";
         str += prevout.ToString();
         if (prevout.IsNull())
             str += strprintf(", coinbase %s", HexStr(scriptSig).c_str());