Added Object.defineProperty + needed internal functionality:

Added Object.defineProperty + needed internal functionality:
  DefineOwnProperty (changed to allow for redefinition of existing property)
  SameValue
  Extra info on propertydescriptor
  GetProperty
  HasProperty

Currently the DefineOrRedefineAccessorProperty deletes the existing
property on the object if it is a dataproperty (FIELD or NORMAL) and
adds a new one. This can potentially be optimized.

Review URL: http://codereview.chromium.org/555149

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@3786 ce2b1a6d-e550-0410-aec6-3dcde31c8c00