A few changes to cleanup the code.

  - Added the header access/heapam.h.
  - Changed all instances of "length" to "data_length" to quiet
    the compiler.
  - initialized a few variables.  The compiler couldn't see that
    the code guaranteed that these would be initialized before
    being dereferenced.  If anyone wants to check my work follow
    the usage of these variables and make sure that this true
    and wasn't actually a bug in the original code.
  - added a missing break statement to a default case.  This
    was a benign error but bad style.
  - layed out heap_sysattrlen differently.  I think this way
    makes the structure of the code crystal clear.  There should
    be no actual difference in the actual behaviour of the code.

Submitted by: darcy@druid.druid.com (D'Arcy J.M. Cain)