arrow function syntax simplified

[Brendan Eich]

http://wiki.ecmascript.org/doku.php?id=strawman:arrow_function_syntax

Use => only with an expression body (do-expressions if accepted allow 
statements and combined with => compete with block-lambdas).

Use -> only with body block, as for long-form function.

I deferred other accretions.

In a rush here, comments and corrections welcome and I'll edit as I can.

/be