Fix FromPropertyDescriptor function

[kkristof]

In the function ecma_op_from_property_descriptor the forth section is unreachable.
FromPropertyDescriptor 8.10.4

The function is needed by the Object.getOwnPropertyDescriptor builtin function 15.2.3.4.

[ruben-ayrapetyan]

Blocks #34

[ruben-ayrapetyan]

Fixed. 5c76b3f.
The condition, checking type of property descriptor was incorrect: instead of checking the type of input descriptor, the type of locally created descriptor was checked.