doc: add note about key derivation

adds a note to the crypto docs passing along
the advice that openssl gives about what
key derivation function they recommend.

PR-URL: https://github.com/joyent/node/pull/8580
Reviewed-By: Fedor Indutny <fedor@indutny.com>
Merge remote-tracking branch 'joyent/v0.10' into v0.10
doc: update openssl commands to use best practices

This updates key size to 2048 and default hash function to sha256.

Reviewed-By: Fedor Indutny <fedor@indutny.com>
PR-URL: https://github.com/joyent/node/pull/8690
doc: clarify dns.lookup vs dns.resolve

Clarify and emphasize the differences between dns.lookup and the rest of
the functions in the dns module.

PR-URL: https://github.com/joyent/node/pull/8726
Reviewed-by: Chris Dickinson <christopher.s.dickinson@gmail.com>
doc: remove wrong spawn error checking example

The example is not correct, and hasn't been since at least v0.10. Exec
errors are emitted as an error event, and documented as such in the
'error' event section.
doc: remove wrong note about spawn env

env was documented as not being process.env under some condtions, which
is no longer correct.
doc: spawn cwd default is current working dir

Default was perhaps obvious, but not documented.
doc: hyperlink and re-order spawn documentation

The lack of hyperlinks requires scrolling past pages of examples to find
the options documentation, the default value of the 'stdio' option was
not documented, and the documentation was not ordered readably.
doc: add the missing ChildProcess.stdio property
doc: ending child_process.stdin does not terminate

Someone must have been confused by how pipes work, but this explanatory
text is worse than nothing, it implies that ending stdin will cause
child processes to terminate, which isn't true for the vast majority of
them.
doc: encoding option for fork does not exist