Uncaught exceptions from aton()

[Paul J. Lucas]

During my elimination of NumConversions and introduction of the aton() function, there are now cases in the code where the exceptions possibly thrown by aton() are not caught, e.g.:

random_impl.cpp: 48, 80

It's possible that the seed value could overflow xs:unsignedInt and range_error be thrown. The old code I replaced silently ignored any overflow. That may in fact be OK, but I don't know the code well enough to make that determination.

Of course, IMHO, this code ideally shouldn't convert to a string and then parse the string back to an integer in the first place.