Repeated member of object literal should be syntax error in strict mode

[mhegazy]

per ECMA-262 11.1.5 Object Initialiser If previous is not undefined then throw a SyntaxError exception if any of the following conditions are true

a. This production is contained in strict code and IsDataDescriptor(previous) is true and IsDataDescriptor(propId.descriptor) is true.
b. IsDataDescriptor(previous) is true and IsAccessorDescriptor(propId.descriptor) is true.
c. IsAccessorDescriptor(previous) is true and IsDataDescriptor(propId.descriptor) is true.
d. IsAccessorDescriptor(previous) is true and IsAccessorDescriptor(propId.descriptor) is true and either both previous and propId.descriptor have [[Get]] fields or both previous and propId.descriptor have [[Set]] fields
.

[vladima]

fixed in #217