Change daemoncore handler tables into dynamically-resizeable arrays. #4206

The arrays comTable, sigTable, and reapTable were statically allocated
with many more entries than are typically used. Now they dynamically
resizeable with a small initial size.
One potential drawback is that lookup time is now linear. If that is an
issue, we could keep the entries sorted and do a binary search for
lookup.
Reduce internal fragmentation in daemoncore handler structs. #4206

Change the layout of the handler structs so that they they are more
compact.
Fix some mismatched arguments for daemon-core CommandHandlers.
Shrink space used by priv-switching history. #4206
Compact the HashTable class to remove internal fragmentation.
Merge branch 'V8_1-gt4206-daemoncore_diet'