udp_wrap: don't use namespace imports in header

It's not really harmful but it's inconsistent with the other header
files.
udp_wrap: use proper imports in source file
stream_wrap, udp_wrap: add read-only fd property

Expose the file descriptor as a read-only property on the internal
handle objects. Intended for debugging purposes, not part of the API
proper. The property is always null on Windows.

Fixes #4754.
bench: Add common script
bench: Add ab() method to common for http testing
bench: add runner
bench: A compare script for analyzing benchmarks
bench: Move net-pipe into benchmark/net
bench: net benchmarks using common script
bench: Remove throughput (covered by benchmark/net)
bench: Remove client_latency

No one actually knows what this is supposed to be doing,
anyway.  It's not a good benchmark.
bench: http benchmarks

Also: make http_simple less chatty
bench: misc/url
bench: misc/startup.js
bench: buffer-base64-encode
bench: Buffer creation
bench: Buffer read/write benchmarks
bench: Merge fast_buffer_creation and buffer_creation
bench: Remove unused 'fast_buffer2' benchmarks
bench: Add buffers/dataview_set