process: document kill(0), disallow kill(O_RDWR)

The null signal test existed, but only tested the case where the target
process existed, not when it did not exist.

Also clarified that SIGUSR1 is reserved by Node.js only for receiveing,
its not at all reserved when sending a signal with kill().

kill(pid, 'O_RDWR'), or any other node constant, "worked". I fixed this
by also checking for 'SIG'. The same as done in the isSignal() function.
Now the signal names supported by process.kill() are the same as those
supported by process.on().
doc: change constant to consistent
doc: list execArgv option for child_process.fork()
tls: fix pool usage race

When calling `encOut` in loop, `maybeInitFinished()` may invoke
`clearOut`'s loop, leading to the writing of interleaved data
(encrypted and cleartext) into the one shared pool.

Move `maybeInitFinished()` out of the loop and add assertion for
future.
blog: bnoordhuis departure
crypto: Make Decipher._flush() emit errors.

When Decipher processes a stream using an incorrect key, the
DecipherFinal() method throws an unhandled exception at the end of the
stream.
doc: document 'error' event for stream.Writable

fix #5255
doc: mention execArgv in setupMaster
build: ./configure pass positional args to gyp

use `--` to specify the arguments you want to pass directly to gyp.

for example: `./configure -- --no-parallel -Dsome_define=foo`

fixes #6370
build: pass --no-parallel by default to gyp

gyp by default now tries to process gyp files in parallel by using
python's multiprocessing module, but it has problems on oddball
platforms. We don't have many files or complex dependency chains that
would benefit from parallel processing so disable by deafult

fixes #6640
Merge remote-tracking branch 'upstream/v0.10'

Conflicts:
	lib/tls.js
	src/node.js
build: older pythons don't support ternary if
crypto: support GCM authenticated encryption mode.

This adds two new member functions getAuthTag and setAuthTag that
are useful for AES-GCM encryption modes. Use getAuthTag after
Cipheriv.final, transmit the tag along with the data and use
Decipheriv.setAuthTag to have the encrypted data verified.