+ some docs update on events


ndb/examples/ndbapi_simple_example/ndbapi_simple.cpp:
  updated example somewhat
ndb/include/ndbapi/NdbDictionary.hpp:
  fixed some docs
ndb/src/ndbapi/NdbDictionary.cpp:
  last go at enabling using const NdbDictionary didn't work
ndb/tools/desc.cpp:
  last go at enabling using const NdbDictionary didn't work
ndb/tools/listTables.cpp:
  last go at enabling using const NdbDictionary didn't work