streams: set listener first, emit 'data' later

When switching into compatibility mode by setting `data` event listener,
`_read()` method will be called immediately. If method implementation
invokes callback in the same tick - all emitted `data` events will be
discarded, because `data` listener wasn't set yet.
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