request.end() would sometimes try to write a zero-length buffer to the socket.
Don't do that, it triggers an unnecessary EPIPE when the other end has closed
the connection.

Fixes #3257.

Before this commit, process._getActiveHandles() returned a list of internal
handles. Now, it returns the user objects that handles are attached to.

For example, a tcp_wrap handle will now return its parent net.Socket object.

It works for all handle types except timers because timer handles are shared
across multiple user objects.

* process._getActiveHandles() returns a list containing all active handles
  (timers, sockets, etc.) that have not been unref'd.

* process._getActiveRequests() returns a list of active requests (in-flight
  actions like connecting to a remote host, writing data to a socket, etc.).

Share persistent strings process_symbol and domain_symbol across compilation
units. Avoids redefinition errors when src/node.cc includes src/req_wrap.h.

Consistent with how other classes that are built around HandleWraps call it.

child_process.fork() support sending native hander object, this patch add support for sending
net.Server and net.Socket object by converting the object to a native handle object and back
to a useful object again.

Note when sending a Socket there was emitted by a net Server object, the server.connections
property becomes null, because it is no longer possible to known when it is destroyed.

This frees us from manually having to copy over functions to SlowBuffer's
prototype (which has bitten us multiple times in the past).

As an added bonus, the `inspect()` function is now shared between Buffer
and SlowBuffer, removing some duplicate code.

Closes #3228.

Idle UDP sockets (reading nor writing) should not keep the event loop alive.
This will get fixed in v0.8 one way or the other.

Make a copy of the options object that the user passes in, we modify it.

Add a better 'is object?' check, the old one let values like true slip through.

Earlier string write optimizations broke it.

In case of an UNWRAP failure, the binding returns -1, which is truthy.

BUG=
TEST=

Review URL: https://chromiumcodereview.appspot.com/10332054

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@11527 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

_snprintf() doesn't zero-terminate the buffer on overflow. Use the hand-rolled
version that lives in src/node_internals.h.

Add a clear warning about known issues with the module and a pointer to the
GitHub issues list for the module. Describe some of the biggest known issues
with the module.

Closes #3201.

Somehow this got downgraded in the last v0.6 merge.  Very strange.

This is an incredibly useful thing to know about, and it
will likely never change.  I can't remember why we
didn't ever document it, and people keep suggesting we
do so.

Regarding discussion in #3198.  Passing the worker as an argument
to an event emitted on the worker is redundant, and an unnecessary
break in consistency vs the events on the ChildProcess objects.

It was removed from 'exit', but 'listening' and others were
overlooked.  This corrects that oversight.

It's too slow.

Make the configure script warn the user about the lack of an acceptable
C compiler on the system.

Fixes #3209.

Fixes #3223.