Apart from this Makefile hack, all I've done is to make dynamically
loaded code modules fail properly (as was already done for __mips__,
although I think this is too loose: I believe NetBSD for the pmax can
do dynamic linking), and to add test-and-set lock handling.  As Bruce
suggested, this is done in a maximally efficient inlined way: I was
not aware that this code was so important, speed-wise.