Does the environment have full property descriptor support? Handles IE 8's broken defineProperty/gOPD.
Returns true if a value has the characteristics of a valid JavaScript descriptor. Works for data descriptors and accessor descriptors.
Returns true if a value has the characteristics of a valid JavaScript accessor descriptor.
Returns true if a value has the characteristics of a valid JavaScript data descriptor.
Gets the description of a Symbol. Handles Symbol()
vs Symbol('')
properly when possible.