Raise a TypeError when the argument to send() or sendto() is anything
but a Buffer.
Fixes the following assertion:
$ node -e 'require("dgram").createSocket("udp4").send("BAM")'
node: ../../src/udp_wrap.cc:220: static v8::Handle<v8::Value>
node::UDPWrap::DoSend(const v8::Arguments&, int): Assertion
`Buffer::HasInstance(args[0])' failed.
Aborted (core dumped)
Fixes#4496.
test/simple/test-url.js:31:(0110) Line too long (82 characters).
test/simple/test-url.js:39:(0110) Line too long (85 characters).
test/simple/test-url.js:40:(0110) Line too long (92 characters).