Additional work on dynamic memory allocation/deallocation.

This should have no effect on smartctl, but clears that way
for smartd to dynamically add and remove entries.  It should
also now be easier to modify smartd to re-read its config
file on HUP (which is easy) without leaking memory (which is
harder). The philosophy is that memory for data structures in
smartd is now allocated only on demand, the first time it
is needed.


git-svn-id: https://smartmontools.svn.sourceforge.net/svnroot/smartmontools/trunk@882 4ea69e1a-61f1-4043-bf83-b5c94c648137