Port to libusb-0.9.0 (synchronous I/O)

Straightforward port to libusb-0.9.0 sync I/O functions, to give libusb-1.0
a bit of a test drive and to create a reference point for later.

libfprint/data.c

@@ -19,6 +19,7 @@
 
 #include <config.h>
 #include <errno.h>
+#include <stdlib.h>
 #include <string.h>
 #include <sys/types.h>
 #include <sys/stat.h>