Initialize the random generator for the internal guid generator

When uuid/uuid.h is not available, mkntfs uses a home-made guid
generator. Better initialize the random generator to get a random guid.

libntfs-3g/security.c

@@ -367,6 +367,8 @@ void ntfs_generate_guid(GUID *guid)
 	unsigned int i;
 	u8 *p = (u8 *)guid;
 
+	/* this is called at most once from mkntfs */
+	srandom(time((time_t*)NULL) ^ (getpid() << 16));
 	for (i = 0; i < sizeof(GUID); i++) {
 		p[i] = (u8)(random() & 0xFF);
 		if (i == 7)