* Plain buffers still inherit from ArrayBuffer.prototype.
* Plain buffers won't object coerce, so Object(plainBuffer) fails.
* All buffer object related methods throw an error; their function bodies
are essentially empty. Note that this includes bindings such as
String.fromBuffer(), ArrayBuffer.allocPlain(), ArrayBuffer.plainOf(),
and so on. In essence, you can index plain buffers in Ecmascript but
the buffer values must be created via the C API.
* Duktape custom bindings like Duktape.dec('hex', 'deadbeef') still work
and produce plain buffers.
Change handling of plain buffers so that they behave like ArrayBuffer
instances to Ecmascript code, with limitations such as not being
extensible and all properties being virtualized. This simplifies
Ecmascript code as plain buffers are just lightweight ArrayBuffers
(similarly to how lightfuncs appear as function objects). There are
a lot of small changes in how the built-in objects and methods, and
the C API deals with plain buffer values.
Also make a few small changes to plain pointer and lightfunc handling
to improve consistency with how plain buffers are now handled.
Improve readability by doing the following renames:
* duk_hcompiledfunction -> duk_hcompfunc
* duk_hnativefunction -> duk_hnatfunc
* duk_hbufferobject -> duk_hbufobj
Corresponding renames for all caps defines.