Support files larger than 2147483647 bytes on 32-bit platforms.

Fixes issue #152.

host/hackrf-tools/src/hackrf_sweep.c

@@ -35,6 +35,8 @@
 #include <fftw3.h>
 #include <math.h>
 
+#define _FILE_OFFSET_BITS 64
+
 #ifndef bool
 typedef int bool;
 #define true 1

host/hackrf-tools/src/hackrf_transfer.c

@@ -34,6 +34,8 @@
 #include <fcntl.h>
 #include <errno.h>
 
+#define _FILE_OFFSET_BITS 64
+
 #ifndef bool
 typedef int bool;
 #define true 1