child_process: remove .track option

Since net.Server's `connection` property is deprecated now, we don't
need API to track socket's state to keep `connection`s value up-to-date.
typed arrays: fix DataView endianness regression

Fix an off-by-one error introduced in 9fe3734 that caused a regression
in the default endianness used for writes in DataView::setGeneric().

Fixes #4626.
dtrace: fix generation of v8 constants on freebsd

Every constant is certainly 4 bytes now, but freebsd's objdump utility
prints out odd byte sequences (5-bytes, 6-bytes and even 9-bytes long)
for v8's data section. We can safely ignore all upper bytes, because all
constants that we're using are just `int`s. Since on all supported
platforms `int` is 32bit long (and anyway v8's constants are 32bit too),
we ignore all higher bits if they were read.
gyp: fix build with dtrace support on FreeBSD

Fix undefined reference to `gelf_getsym`... and other undefined symbols
from libelf, by adding `-lelf` to linker options on FreeBSD.
doc: Fix syntax in cluster example code