process_wrap: update after libuv api change
process_wrap: update after libuv api change

The `exit_code` argument for the `ProcessWrap::OnExit` callback changed
from int to int64_t.

dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node