doc: document max `new Buffer(size)`

Signed-off-by: Timothy J Fontaine <tjfontaine@gmail.com>
test: fix test-process-kill-pid on Windows

Disabling the part of the test that relies on dispatching SIGHUP,
because sending SIGHUP is not supported on Windows.

Signed-off-by: Timothy J Fontaine <tjfontaine@gmail.com>