Update for Libuv v1.52.0

[squeek502]

https://github.com/libuv/libuv/releases/tag/v1.52.0

[truemedian]

A quick glance says that the only things of interest here are the new uv_udp_open_ex function, which accepts flags versus uv_udp_open and f_frsize in uv_statfs_t. Likely useful for us to bind.

Everything else seems to be bug-related.

Edit: Missed uv_tcp_keepalive_ex