make sure that the 'struct malloc' header on allocations is properly
aligned to (ALIGNBYTES+1).  this ensures that the memory that malloc(9)
returns is correctly aligned for the platform.  this change has an
effect on hppa, ia64, sparc and sparc64.

necessary on sparc for 8-byte load/store instructions.  with this my
SS20 boots multiuser again.

(mrg)