VM must ensure static methods and top level functions are constants

[gbracha]

Per the latest 0.10 spec draft, section 10.1; please implement.

[DartBot]

This comment was originally written by @mhausner

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Set owner to @mhausner.
Added Started label.

[DartBot]

This comment was originally written by @mhausner

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Implemented at r10600.

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Added Fixed label.