DWDS/Dialing Concordance Code

* removed old hard-codced 500MB limit on size of *._TOKATTR (string-buffer) in IndexSetForLoadingStage.cpp
- now use macro MAX_STRINGBUFFER_SIZE = (DWORD_MAX & (~AllFlags)) --> 2GB
- fixed limit check (the actual exception was previously only catching on 1st insertion after overflow)
* debugging for v1.x->v2.x index upgrade

* added missing m_ServerStats.m_xTimes.Scrub() in *Server::handle__status(): EMA decay
* fixed typo in LeafServer::handle__status(): xtavg keys was actually reporting qtavg
* EMA tweaks in DDCTimeAvg
- redefined DDCTimeAvg::TimeT as DDCTimeHiRes: use high-resolution clock if available for EMA
- handle counter overflow in DDCTimeAvg::Append()
- use current timestamp TimeT::Now() for DDCTimeAvg::operator+=(): avoid out-of-order insertions

+ corrected info message typo in ConcordUnion.cpp

+ SIZE_MAX hack for gcc 4.7.2 (kaskade, debian wheezy)

+ typo fix in doc/ddc_proto.pod

+ tagged DDC-Concordance-0.42

+ tagged DDC-XS-0.21

+ tagged ddc-2.1.16

+ tagged DDC-Concordance-0.42-rc3

+ stringification of comments before subcorpora