Add a performance todo, remove a duplicate.

TODO.md

@@ -25,13 +25,13 @@ const zip_uint8_t *zip_get_archive_prefix(struct zip *za, zip_uint64_t *lengthp)
 
 # Features
 
+* performance: read local directory later when copying files from zip to zip
 * set version needed correctly
 * Winzip AES support
   * test cases decryption: <=20, >20, stat for both
   * test cases encryption: no password, default password, file-specific password, 128/192/256, <=20, >20
   * support testing on Linux
   * support testing on macOS
-* xz support
 * consistently use `_zip_crypto_clear()` for passwords
 * implement compression flags for `zip_set_file_compression()`
 * support setting extra fields from `zip_source`