Update parsePropertyFunction and parsePropertyMethodFunction to use parseParams.
Update parsePropertyFunction and parsePropertyMethodFunction to use parseParams.

These functions already pass around some state of there own due to some information living outside
of the function expression they contain.

* The parameter state object is now used also for property method state.
* Redundent parameter checking removed in favor of using the centralized parseParams.

http://code.google.com/p/esprima/issues/detail?id=377

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