DWDS/Dialing Concordance Code

* more count() tweaks and fixes
- generally working for ddc_simple, even with multiple count-keys and date-slicing via stupid string hacks
- still todo: work into distributed server

+ got basic counting-code inserted
- still very ugly and ad-hoc
- no server integration yet, just up to leaf-node GetHitIds() (server request get_firs_hits9
- looks like we'll have to actually parse things in the server as well in order to get server-level merging going on

+ tweaked root-level query filters and flags into CQueryOptions

* fixed missing m_ErrorStr.clear()

+ fixed segfaults after making filters query-local
- problem was CConcHolder::GetAllHits() calling CQueryCompiler::DeleteTree()

+ argh: segfaults in simple '@Haus' queries

+ v2.0.23: updated Changes and doc/ddc_proto.pod

+ re-factored old monolithic src/ConcordDmnLib/Corpora.cpp into
Server.(h|cpp) : abstract server base class
LeafServer.(h|cpp) : subcorpus server, formerly CDDCCorpusListenHost
BranchServer.(h|cpp) : distributed server, formerly CDDCServerListenHost
+ added 'reload' server message
+ unified (leaf|branch) message parsing code and syntax
+ TODO: implement leaf-node commands (get_first_hits, get_hit_strings) for branch-node servers

+ configure.ac : set version 2.0.22-1 (stale)

+ ignore ddc.pc