Define HeapEnableTerminationOnCorruption if the headers don't.

MSDN says that it's always going to be 1, and they're usually pretty
accurate about that.

Fixes a bug in 21953.

src/or/main.c

@@ -3426,6 +3426,9 @@ tor_main(int argc, char *argv[])
   int result = 0;
 
 #ifdef _WIN32
+#ifndef HeapEnableTerminationOnCorruption
+#define HeapEnableTerminationOnCorruption 1
+#endif
   /* On heap corruption, just give up; don't try to play along. */
   HeapSetInformation(NULL, HeapEnableTerminationOnCorruption, NULL, 0);
   /* Call SetProcessDEPPolicy to permanently enable DEP.