kernels, at the same time getting rid of up to 3 conditional branches and a
bit over one cacheline fetch (for the 68060; the saving is a bit smaller for
040 and yet smaller for the 020/30).
While we're here, also get rid of an redundant lea (using SP-relative
addressing) and of two redundant pushes.
While we're here, also fix a panic which would tear us down on 68060 machines
if a branch prediction error ever occured.
6d6e724440