fsck.gfs2: rgrp block count reform
    
    In the past, pass5 has kept track of different counts for the different
    metadata types, but the counts did not correspond to the type in the
    bitmap. This patch changes pass5 so that it makes a little more sense.
    There should be a straightforward blockmap-to-bitmap conversion, and
    the counts should be based on the bitmap type. For example, before the
    patch, the rgrp's inode count would be kept in count[1], but in the
    bitmap, dinodes are of type 3. So this patch reworks that system so
    that the count of dinodes is kept in count[3] and so forth, and it
    uses a simple blockmap-to-bitmap to figure out the index to "count".
    This breaks down for GFS1 which keeps a few extra numbers in the rgrp,
    however this patch compensates for that. This patch is being done
    as a precursor to another patch that reduces fsck's memory requirements
    by using a blockmap that's 1:1 with the bitmaps rather than today's
    blockmap that's 4:1.