Port enough of libuv to HP-UX 11.31 ia64 with GCC 4.9.3 to work for CMake.
* upstream-libuv: libuv 2019-06-10 (ee24ce90)
Headers in `uv/` can include each other without the `uv/` prefix. Using the prefix assumes that the location of `uv/` is in the include file search path, but it is possible to include `uv.h` via a longer path.
* upstream-libuv: libuv 2019-01-15 (f84c5e69)