Fix warning on 32bit.

cgminer.c

@@ -238,7 +238,7 @@ static char datestamp[40];
 static char blocktime[32];
 struct timeval block_timeval;
 static char best_share[8] = "0";
-double current_diff = 0xFFFFFFFFFFFFFFFF;
+double current_diff = 0xFFFFFFFFFFFFFFFFULL;
 static char block_diff[8];
 uint64_t best_diff = 0;