build: vcbuild.bat fix for Visual Studio 2012

Change vcbuild.bat to ignore VCINSTALLDIR environment variable,
always check for specific VS version and set GYP_MSVS_VERSION
accordingly. Otherwise GYP generates project files in format
that cannot be compiled by VS2012.
Merge branch 'v0.10'
build: only use DESTDIR instead of PREFIX for pkg

Preserve default install prefix seen in process.config, but use DESTDIR
for installing to deliniate 32/64 versions, avoid conflicts with PREFIX
settings in config.mk
test: reap children when cluster-bind-twice fails
test: report test duration in TAP progress
stream_wrap: remove unused arg from WriteBuffer

WriteBuffer was changed in the cork/uncork implementation (60ed2c54).
The unused argument has been removed.
stream_wrap: fix memory leak on early return
test: don't use total_seconds() because of py2.6
debugger, cluster: each worker has new debug port

Implement support for debugging cluster workers. Each worker process
is assigned a new debug port in an increasing sequence.

I.e. when master process uses port 5858, then worker 1 uses port 5859,
worker 2 uses port 5860, and so on.

Introduce new command-line parameter '--debug-port=' which sets debug_port
but does not start debugger. This option works for all node processes, it
is not specific to cluster workers.

Fixes joyent/node#5318.
src: initialize debug-related uv_async_t handles

uv_async_t handles for dispatching of debug messages and
emitting NODE_DEBUG_ENABLED used to be initialized every time
node::EnableDebug() was called, which happened every time
user sends a SIGUSR1.

Now they are initialized only once from node::Init() during
application start.