windows: fix stat("c:\\") regression

Fix windows build

unix: turn on SO_REUSEPORT for UDP sockets

Required on BSD-like systems for local UDP multicast. Without it, the bind()
call fails with EADDRINUSE.

unix: implement uv_udp_set_multicast_loop()

unix: implement uv_udp_set_ttl()

Add missing UV_EXTERN declarations in uv.h

Windows: add error mapping for WSAENOBUFS

Windows: Add support for interpreting axiterm-style colors.

unix: map `ENAMETOOLONG` to `UV_ENAMETOOLONG`

With tests. Closes #295

windows: set error using WSAGetLastError

implement uv_udp_set_multicast_ttl and uv_udp_set_broadcast on windows

unix: add uv_udp_set_broadcast() and uv_udp_set_multicast_ttl()

unix: set SO_REUSEADDR before binding

build: don't set -mmacosx-version-min

It sets __MAC_OS_X_VERSION_MIN_REQUIRED__, which is what we use for feature
detection.

build: generate Makefiles on OS X

unix: don't close kqueue fd in kqueue_fork()

The file descriptor is not inherited by the child process. Trying to close it is
not just useless, it's actively harmful - if the close() cal

unix: don't close kqueue fd in kqueue_fork()

The file descriptor is not inherited by the child process. Trying to close it is
not just useless, it's actively harmful - if the close() call succeeds, it will
have closed an altogether different file descriptor.

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unix: fix segfault in uv_guess_handle()

Fixes #293.

unix: fix udp recv_start refcount

Calling uv_udp_recv_start() should not bump the event loop's reference count.

Fixes failing test udp_ref2.

Add uv_loop_refcount() function, debug tool.

test: add lots of refcount tests

test: add udp4_echo_server helper

unix: remove unused #define

unix: fix compiler warning

windows: improve uv_fs_stat performance (by about 60%)

linux: fix build on older distros