Log Message:
libfilezilla: update to 0.20.2.

0.20.2 (2020-03-10)

+ Add encrypt_key and decrypt_key to fz::symmetric key
- fz::datetime::set_rfc822 now parses the zone offset
- Removed unneeded asserts from format.hpp

0.20.1 (2020-02-24)

- Fix potential crash after removing the last speed limit bucket
- TLS: Fix reported key exchange algorithm and improve details

0.20.0 (2020-02-14)

+ Added fz::symmetric_key
+ Added itertions parameter to fz::private_key::from_password
+ Added fz::base32_encode and fz::base32_decode
+ Unified all decode functions to always return a vector, added alternatives \ 
returning string with a _s suffix in the function name
+ Changed equal_insensitive_ascii to take (w)string_view