unix, windows: add uv_fs_mkdtemp
build: handle platforms without multiprocessing.synchronize
windows: change GENERIC_ALL to GENERIC_WRITE in fs__create_junction

Fixes #1385

See ReactOS's mklink implementation and
http://stackoverflow.com/a/10508724
windows: relay TCP bind errors via ipc

This is the libuv side of the fix for Node's cluster module on Windows.
https://github.com/joyent/node/issues/7691

Windows and Unix return certain socket errors (i.e. EADDRINUSE) at
different times: bind on Windows, and listen on Unix.
In an effort to hide this difference, libuv on Windows stores such
errors in the bind_error field of uv_tcp_t, to defer raising it at
listen time.
This worked fine except for the case in which a socket is shared in
a Node cluster and a bind error occurs.

A previous attempt to fix this (
https://github.com/joyent/libuv/commit/d1e6be1460f555a1f8a4063d7642696aa7238769
https://github.com/joyent/node/commit/3da36fe00e5d85414031ae812e473f16629d8645
) was flawed becaused in an attempt to relay the error at the JS level
it caused the master to start accepting connections.

With this new approach, libuv itself is relaying the bind errors,
providing for a uniform behavior of uv_tcp_listen.