* Change plain buffers to inherit from Uint8Array. This affects a lot of
small things like Object.prototype.toString() output, enumeration of plain
buffers, etc. It also changes JSON serialization for plain buffers because
the index properties are enumerable as with Uint8Array instances.
* Disable JSON stringify fastpath for plain buffers for now so that the
virtual index properties get serialized correctly.
* Remove ArrayBuffer non-standard virtual properties.
* Remove DataView non-standard virtual properties.
* Move .byteLength, .byteOffset, .BYTES_PER_ELEMENT, and .buffer into
inherited getters as required in ES6. However, the .length property
remains a virtual own property for now (it too is an inherited getter
in ES6).
* Move ArrayBuffer.allocPlain() and ArrayBuffer.plainOf() to
Uint8Array.allocPlain() and Uint8Array.plainOf() to match the
semantics change for plain buffers.
* Fix Node.js buffer .slice() behavior, the returned Node.js buffer
would have ArrayBuffer.isView == 0 which doesn't match the revised
Node.js behavior (Buffers being Uint8Array instances)
* Reject ArrayBuffers with a view offset/length in Node.js Buffer .slice()
rather than accept such ArrayBuffers without actually respecting the
view offset/length.
* Allow a plain buffer or a lightfunc as a constructor "replacement object"
return value.
* Comment on duk_buffer_to_string() safety w.r.t. potentially pushing
Symbol values.
* Went through all duk_push_(l)string() call sites too.
* Minor footprint optimization for pushing empty strings (use more
compact internal helper).