pthread_attr_setstacksize() expects that the stack size is a multiple of
the page size so make sure that it is.
Fixes a regression introduced in commit 3db07cc ("osx: set the default
thread stack size to RLIMIT_STACK") that made the program abort under
certain configurations; GNU Emacs on OS X apparently sets RLIMIT_STACK
to odd values when executing child processes.
Fixes: https://github.com/nodejs/node/issues/6563
PR-URL: https://github.com/libuv/libuv/pull/864
Reviewed-By: Saúl Ibarra Corretgé <saghul@gmail.com>
28d160f3de