Problems with NSAffineTransform

[Fred Kiefer]

I just found the reasion for bug #19301. Richard has added some
optimisation for NSAffineTransform to base. This optimisation relies
heavily on the flag _isIdentity to be correctly set on the
NSAffineTransform. This was taken care of in the base methods, but not
in the methods still in the gui code for this class. Of course
operations with this class now fail completely in gui as back uses only
these gui methods. I have fixed this by setting this flag to NO in gui
for almost all methods. Of course this will remove the whole
optimisation for most cases. I think the best way out of here is to
change back to use the methods defined in Foundation instead of our own
ones.

Of course this change needs to be backported to the stable branch, no
idea how to do this. Best we delay the next GNUstep release anyway until
we are sure this problem has been fixed completely.

Cheers,
Fred