KVO bug

[Kevin Fox]

I just spent the last few hours trying to figure out why my code, that
satisfied all the requirements in the Apple KVC and KVO documents would
work using GNUStep base with KVC but not with KVO. Issuing:

[eye addObserver:self forKeyPath:@"x"
options:NSKeyValueObservingOptionNew context:NULL];

would print out an error message:
class eye not KVC complient for x

It turns out if setX returns anything but void, gnustep base bails. This
seems like incorrect behavior since the docs don't say anything about
this requirement.

Thanks,
Kevin