Further merging of SharedArrayBuffer and ArrayBuffer in the spec prose

[lars-t-hansen]

In Issue #89, @leobalter suggested that after simplifying SharedArrayBuffer by naming its internal properties the same as for ArrayBuffer, we could go further:

"Following the same reuse idea, the API for SharedArrayBuffer constructor and properties could be defined as in %TypedArray%.prototype methods: "ShareArrayBuffer is a distinct function that implements the same algorithm as ArrayBuffer as defined in 24.1.2.1 except that AllocateSharedArrayBuffer is called instead of AllocateArrayBuffer._"

That is helpful to keep both methods with the closest seamless implementation, especially when there's a chance to change ArrayBuffer in tc39/ecma262#410. This is also help on properties as byteLength, slice, etc."

At the moment, the original simplification (property names) has been done but this is a separate idea.

[lars-t-hansen]

I'm going to close this since the spec prose has been merged and what we say here has no impact on the merged prose. @leobalter, if you still like this idea I think you should reopen as issue against ecma262.