contextify: remove useless header file

fix #7910
streams: set default hwm properly for Duplex

Default highWaterMark is now set properly when using stream Duplex's
writableObjectMode and readableObjectMode options.

Added condition to the already existing split objectMode test to ensure
the highWaterMark is being set to the correct default value on both the
ReadableState and WritableState for readableObjectMode and
writableObjectMode.

Signed-off-by: Fedor Indutny <fedor@indutny.com>
lib: noisy deprecation of child_process customFds

Use a util.deprecate wrapper to issue warnings like any other
deprecated API. The option has been marked as deprecated in the docs
since v0.5.11.

Signed-off-by: Fedor Indutny <fedor@indutny.com>
doc: remove customFds mentions

The feature has been marked as deprecated since v0.5.11.

Signed-off-by: Fedor Indutny <fedor@indutny.com>
test: Remove references to customFds

Option has been deprecated since v0.5.11

Signed-off-by: Fedor Indutny <fedor@indutny.com>
doc: re-org child_process into async/sync

Cleaner separation between the traditional non-blocking functions and
the new blocking variants.

Signed-off-by: Fedor Indutny <fedor@indutny.com>
cluster: allow multiple calls to setupMaster()

Only attributes of 'cluster.settings' will be modified after the first
call, leaving all other cluster initialization alone. Each call that
includes a 'settings' argument triggers a 'setup' event to be emitted.

Test for multiple emits of 'setup' event.
cluster: include settings object in 'setup' event

Emits on every call to cluster.setupMaster(), even if no new settings
are given. This is because calling cluster.setupMaster() without
arguments (or with an empty options object) results in the settings
being restored to their defaults.
cluster: make cluster.setupMaster() cumulative

Instead of each call resetting all values to their defaults, use the current settings (if any) as the default.

This makes the multiple-calls support compatible with cluster.fork()'s use of setupMaster() to ensure cluster.settings has been populated.
doc: Update cluster.setupMaster() example

Update previous example to node coding style and include an example of progressive configuration