test: fix simple/test-http-client-timeout-with-data

The test was failing in debug mode because the timeouts were set too
low. Fix that by increasing the timeouts. Admittedly not a great fix.
If this test keeps playing up, it's probably best to remove it.

Fixes #4528.
node: move symbol caching to Load()
child_process: don't `resume()` created socket

Calling `resume()` on a stream switches it to the old mode which causes
piping stdio from a child process to fail.

Fixes joyent/node#4510.
stream: Clean up more effectively in pipe()
child_process: Pull through untouched stdio streams

Otherwise child procs will never emit a 'close' event if you don't
ever consume their streams, because they will never hit the EOF.
src: make node_isolate global

V8 3.15 has new API functions that let you specify the Isolate. V8 and
node.js generally spend 0.5-3.5% of the time in pthread_getspecific(),
looking up the current Isolate. Avoid that overhead by making "our"
isolate global so we can pass it around. The change to the new API is
introduced in follow-up commits.
src: pass node_isolate to String::Empty
src: pass node_isolate to Integer::New
src: pass node_isolate to Local<>::New
src: pass node_isolate to True() and False()
src: pass node_isolate to Null()
src: pass node_isolate to Undefined()
dtrace: SeqAsciiString was renamed to SeqOneByteString in v8
buffer: floating point read/write improvements

Improvements:
* floating point operations are approx 3x's faster
* Now write quiet NaN's
* all read/write on floating point now done in C, so no more need for
  lib/buffer_ieee754.js
* float values have more accurate min/max value checks