libfilezilla: update to 0.38.1.

0.38.1 (2022-07-20)

+ fz::aio_waitable now also accepts event handlers in addition to aio_waiter
- Split fz::process::kill into separate stop and kill functions

0.38.0 (2022-07-08)

+ Added readers and writers for asynchronous disk I/O operating on a buffer pool
+ Added fz::current_username()
+ Added fz::event_handler::stop_add_timer
+ Added overload for fz::event_handler::add_timer that takes a deadline
+ Added fz::file::set_modification_time
+ Added fz::get_network_interfaces
+ *nix: fz::socket can now accept Unix-domain sockets, added fz::socket::send_fd and fz::socke::read_fd
- *nix: When impersonating, limit supplementary groups to NGROUPS_MAX

(wiz)