Add *NeededBytesAlign(), which overestimates the padding which is later

Add *NeededBytesAlign(), which overestimates the padding which is later
    added by the new ALIGN macro. Fix alignment problems on ia64 and s390
    by bumping up block_ptr appropriately. (Earlier version by Andreas
    Schwab).
Use sysconf to determine proper PAGESIZE value; this appears to be
    POSIX-compliant. (reported by Andreas Schwab)
reviewed by: plam