Provide a real fix to the too-many-translations problem when booting
from CD on 64-bit hardware to replace existing band-aids. This occurred
when the preloaded mdroot required too many mappings for the static
buffer.
Since we only use the translations buffer once, allocate a dynamic
buffer on the stack. This early in the boot process, the call chain
is quite short and we can be assured of having sufficient stack space.
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