[project @ 2004-11-10 03:20:31 by wolfgang]

[project @ 2004-11-10 03:20:31 by wolfgang]
Implement the mblock map for 64-bit architectures.
Fairly primitive data structure, but one 4GB-block, described by a
12-bit block map, is cached for speed.

Note that I've nuked the ia64-specific version (I think ia64 wants to
use the general 64-bit solution, too).