ra144: fix code with ftrapv.

A better solution is welcome!
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavcodec/ra144.c

@@ -1567,8 +1567,14 @@ int ff_eval_refl(int *refl, const int16_t *coefs, AVCodecContext *avctx)
             b = -2;
 
         b = 0x1000000 / b;
-        for (j=0; j <= i; j++)
+        for (j=0; j <= i; j++) {
+#if CONFIG_FTRAPV
+            int a = bp2[j] - ((refl[i+1] * bp2[i-j]) >> 12);
+            if((int)(a*(unsigned)b) != a*(int64_t)b)
+                return 1;
+#endif
             bp1[j] = ((bp2[j] - ((refl[i+1] * bp2[i-j]) >> 12)) * b) >> 12;
+        }
 
         if ((unsigned) bp1[i] + 0x1000 > 0x1fff)
             return 1;