*more* alignment problems

[Richard Kenner]

    Because all of those bitfield functions were manipulating alignment in
    bytes, the SLOW_UNALIGNED_ACCESS macro expects the alignment to be
    bytes.  The primary question for SLOW_UNALIGNED_ACCESS is whether the
    alignment is less than the natural alignment for the type, usually in
    granularity of bytes, not bits.

Why does it matter which way it's defined?  I changed the macro in
rs6000.h to accept bits.