libuv: updated to 1.19.0

Version 1.19.0 (Stable):
* core: add getter/setter functions for easier ABI compat
* unix: make get(set)_process_title MT-safe
* unix,win: wait for threads to start
* test: add threadpool init/teardown test
* win, process: uv_kill improvements
* win: set _WIN32_WINNT to 0x0600
* zos: implement uv_fs_event* functions
* unix,tcp: avoid marking server sockets connected
* doc: mark Windows 7 as Tier 1 support
* win: map 0.0.0.0 and :: addresses to localhost
* build: install libuv.pc unconditionally
* test: remove custom timeout for thread test on ppc
* test: allow multicast not permitted status
* test: allow net unreachable status in udp test
* unix: use SA_RESTART when setting our sighandler
* unix,fs: fix for potential partial reads/writes
* win,build: do not build executable installer for dll
* win: allow directory symlinks to be created in a non-elevated context
* zos,test: accept SIGKILL for flaky test
* win: use RemoveDirectoryW() instead of _wmrmdir()
* unix: fix uv_cpu_info() error on FreeBSD
* zos,test: decrease pings to avoid timeout

(adam)