This can be disabled (to save a bit of space) with the NO_KERNEL_RCSIDS
options, which is present but commented out in the ALPHA config file.
In ELF-format kernels, these strings are present in the kernel binary but
are not loaded into memory. (In ECOFF-format kernels, there's no easy way
to keep them from being loaded, so they _are_ loaded into memory.)
is set in the RPB's rpb_variation field. This fixes a bug where machines
(e.g. the 3000/900) would see that they could touch memory where a built-in
PMAGB-BA, assume that it was there, and panic later because the memory they
were accessing didn't look like PMAGB-BA registers (because it wasn't).
handling code so that if a given interrupt is disabled (and therefore
can't have caused the actual I/O interrupt), its handler won't be
called even if its bit is set in the interrupt register.
