Memory (Windows): adds comments [ci skip]

src/detection/memory/memory_windows.c

@@ -7,6 +7,9 @@ const char* ffDetectMemory(FFMemoryResult* ram)
     MEMORYSTATUSEX statex = {
         .dwLength = sizeof(statex),
     };
+    // GlobalMemoryStatusEx() internally uses
+    // NtQuerySystemInformation(SystemBasicPerformanceInformation) in Win 7, and
+    // NtQuerySystemInformation(SystemMemoryUsageInformation) in Win 10
     if (!GlobalMemoryStatusEx(&statex))
         return "GlobalMemoryStatusEx() failed";