old MSVC versions don't have rdtsc

use _emit instead

Pointed out by Jeremy Cooper <jeremy@baymoo.org>

crypto/rand/rand_win.c

@@ -582,7 +582,8 @@ static void readtimer(void)
 	if (have_tsc) {
 	  __try {
 	    __asm {
-	      rdtsc
+	      _emit 0x0f
+	      _emix 0x31
 	      mov cyclecount, eax
 	      }
 	    RAND_add(&cyclecount, sizeof(cyclecount), 1);