stream: Start out in sync=true state

The Readable and Writable classes will nextTick certain things
if in sync mode.  The sync flag gets unset after a call to _read
or _write.  However, most of these behaviors should also be
deferred until nextTick if no reads have been made (for example,
the automatic '_read up to hwm' behavior on Readable.push(chunk))

Set the sync flag to true in the constructor, so that it will not
trigger an immediate 'readable' event, call to _read, before the
user has had a chance to set a _read method implementation.
stream: Do not switch to objectMode implicitly

Only handle objects if explicitly told to do so in the options
object.  Non-buffer/string chunks are an error if not already in
objectMode.

Close #4662
deps: downgrade v8 to 3.14.5

V8 3.15 and newer have stability and performance issues. Roll back to
a known-good version.
v8: reapply floating patches

Reapply floating patches. Special mention: also reapplies 017009f but
with the extra change of removing DescriptorArray::kTransitionsIndex
from the postmortem metadata generator because said field no longer
exists in V8 3.14.
src, test: downgrade to v8 3.14 api
sunos: unbreak build after v8 downgrade

Commit 3d67f89 ("fix generation of v8 constants on freebsd") is an
unfortunate victim of this rollback.

Revert "dtrace: fix generation of v8 constants on freebsd"
Revert "dtrace: More style"
Revert "dtrace: Make D style more D-ish"
Revert "dtrace: x64 ustack helper"
Revert "dtrace: fix style in ustack helper"
Revert "dtrace: SeqAsciiString was renamed to SeqOneByteString in v8"

This reverts commit 3d67f895521cf905922d20af9b03e5c73c363868.
This reverts commit 321b8eec08d445d60a4149bfa71959936fc189c6.
This reverts commit 38df9d51a229e1d74b2d1c2835353f07c784cfc3.
This reverts commit f9afb3f01002e5667a0df80ee784af0dfe2305c2.
This reverts commit 13296e4b13b5ed192c4faa6501f3efec2ded8ac1.
This reverts commit 3b715edda97c8edfd95cc1fb8d31f92cef6bcc52.
bench: Make http easier to profile

Do not run the http/simple.js server in a child process.

Fix #4831
Revert "sunos: unbreak build after v8 downgrade"

This reverts commit f80f3c5f62a3955636c1af1872ef9539a0b01cb0.
v8: fix postmortem and dtrace helper build

Regardless of previous @bnoordhuis' changes