unix: update events from pevents between polls

Watchers could be stopped between two `kevent()`/`epoll_wait()` calls
(which may happen in the same loop in `uv__io_poll()`), in such cases
`watcher->events` could be stale and won't be updated to
`watcher->pevents`.

Try to use and rely on `watcher->pevents` instead of blindly expecting
`watcher->events` to be always correct.
test: add regression test for 29fdb3471
fsevents: support japaneese characters in path
linux: don't turn on SO_REUSEPORT socket option

On the BSDs, SO_REUSEPORT is pretty much SO_REUSEADDR with some special
casing for IP multicast.  When two processes (that don't do multicast)
bind to the same address, only the last one receives traffic.  It allows
one to "steal" the bound address from another process.  (Both processes
have to enable SO_REUSEPORT though, so it only works in a cooperative
setting.)

On Linux however, it enables port sharing, not stealing - both processes
receive a share of the traffic.  This is a desirable trait but pre-3.9
kernels don't support the socket option and a libuv program therefore
behaves differently with older kernels or on another platform.

This is a back-port of commit 9d60f1e from the master branch.

Fixes joyent/node#6454.
build: fix windows smp build with gyp

Gyp will try a parallel build if it detect the system has >1 processor.
This functionality depends on the Python "multiprocessing" package. The
multiprocessing package on Windows requires that the top-level module is
importable as a module, see:

  http://docs.python.org/2/library/multiprocessing.html#windows

This fixes issue #984.
build: fix windows smp build with gyp

Gyp will try a parallel build if it detect the system has >1 processor.
This functionality depends on the Python "multiprocessing" package. The
multiprocessing package on Windows requires that the top-level module is
importable as a module, see:

  http://docs.python.org/2/library/multiprocessing.html#windows

This fixes issue #984.

This is a back-port of commit 2445467 from the master branch.
unix: return exec errors from uv_spawn, not async

If spawning a process fails due to an exec() failure (but it succeeded
in forking), then this should be considered a spawn failure instead of
an asynchronous termination of the process. This allows to check for
common exec() failure conditions such as a bad path quickly instead of
having to rely on keeping track of the async callback.

Additionally, the meaning of the two fields returned in the callback are
now exactly what they advertise to be. The process exit argument is not
one of two values depending on what happened to the child.

Fixes #978.
Merge remote-tracking branch 'origin/v0.10'

Drops commit 3780e12 ("fsevents: support japaneese characters in path")
for being quite inapplicable to the master branch.  Will be reworked
and applied in a follow-up commit.

Conflicts:
	README.md
	build.mk
	src/unix/fsevents.c
	src/unix/udp.c