Add --keyfile-offset and --new-keyfile-offset to cryptsetup.

Add resume_by_keyfile_offset, add_kesylot_by_keyfile_offset and
activate_by_keyfile_offset to API.

Thanks to Matthew Monaco <matthew.monaco@0x01b.net>

lib/utils_crypt.h

@@ -14,7 +14,7 @@ int crypt_parse_name_and_mode(const char *s, char *cipher,
 
 int crypt_get_key(const char *prompt,
 		  char **key, size_t *key_size,
-		  size_t keyfile_size_max,
+		  size_t keyfile_offset, size_t keyfile_size_max,
 		  const char *key_file,
 		  int timeout, int verify,
 		  struct crypt_device *cd);