fix display of ARRAY fields inside of structure data types.

Previously ARRAY fields in structures were displayed, for example,
like 'ARRAY [1..2] OF ARRAY' instead of 'ARRAY [1..2] OF INT'. Because
of this error the array type can be really edited.

import os
from POULibrary import POULibrary

class NativeLibrary(POULibrary):
    def GetLibraryPath(self):
        return os.path.join(os.path.split(__file__)[0], "NativeLib.xml")