better wallet.dat flush, consolidated QueryPerformanceCounter, PRI64d printf portability

net.h

@@ -589,7 +589,7 @@ public:
         // We're using mapAskFor as a priority queue,
         // the key is the earliest time the request can be sent
         int64& nRequestTime = mapAlreadyAskedFor[inv];
-        printf("askfor %s  %I64d\n", inv.ToString().c_str(), nRequestTime);
+        printf("askfor %s  %"PRI64d"\n", inv.ToString().c_str(), nRequestTime);
 
         // Make sure not to reuse time indexes to keep things in the same order
         int64 nNow = (GetTime() - 1) * 1000000;