New and noteworthy:
1) Introduction of a new "object" which provides a standard way to
allocate like structures in blocks and parcel them out as needed.
Includes methods to allocate, free, and query the space utilization.
The code to support this functionality is housed in struct_manager.[ch].
2) Changed trie nodes, trie hash tables, and answer list nodes over to
the above maintenance object.
3) emuMakefile.in updated to include struct_manager.c
4) More clean-up of macros whose functionality was duplicated or
subsumed by another.
5) Robustified trie-deletion functions:
a) fixed memory leaks--e.g., answer list nodes weren't being deleted
b) number of nodes in hash table was being incorrectly set (count
from IsInsibling) which caused problems in delete_branch.
c) exceptional conditions tested for and reported
6) exception_handler now includes call to switch_from_trie_assert. If
an abort is triggered while assert-trie-space is set as the default
trie-space, then table-trie components could incorrectly be allocated
from assert-trie-space.
