process: pid can be a string in process.kill()

Not allowing string was a change from v0.10 behaviour, commented on in
joyent/node#7991. Allow them again, but still check that argument is
numberish. Also, simplify the fragile and non-portable test code
introduced in 832ec1cd507 that required fixups 2a415358ee, and
ef3c4ed3d.

PR-URL: https://github.com/joyent/node/pull/8531
Reviewed-by: Trevor Norris <trev.norris@gmail.com>
dns: propagate domain for c-ares methods

Fixes: https://github.com/joyent/node/issues/5471
PR-URL: https://github.com/joyent/node/pull/8732
Reviewed-by: Trevor Norris <trev.norris@gmail.com>
doc: fix typos in http.markdown

PR-URL: https://github.com/joyent/node/pull/4784
Reviewed-by: Chris Dickinson <christopher.s.dickinson@gmail.com>
doc: clarify return value of http.createServer

PR-URL: https://github.com/joyent/node/pull/6054
Reviewed-by: Isaac Z. Schlueter <i@izs.me>
Reviewed-by: Chris Dickinson <christopher.s.dickinson@gmail.com>