Fix compilation for Windows 7 with MinGW

src/base/bittorrent/session.cpp

@@ -2924,6 +2924,13 @@ void Session::applyOSMemoryPriority() const
     {
         ULONG MemoryPriority;
     };
+
+#define MEMORY_PRIORITY_LOWEST 0
+#define MEMORY_PRIORITY_VERY_LOW 1
+#define MEMORY_PRIORITY_LOW 2
+#define MEMORY_PRIORITY_MEDIUM 3
+#define MEMORY_PRIORITY_BELOW_NORMAL 4
+#define MEMORY_PRIORITY_NORMAL 5
 #endif
 
     MEMORY_PRIORITY_INFORMATION prioInfo {};