- Fix Catalog JSON table crash when no Jpath

- Added JSON OBJECT specification for pretty != 2.
- Fix NULL values not recognized for nullable JSON columns
- Issue an error message when a JSON table is created without specifying LRECL if PRETTY != 2.
- Make JSONColumns use a TDBJSON class.
- Make JSON table using MAPFAM
modified:
  filamap.h
  filamtxt.h
  ha_connect.cc
  json.result
  tabjson.cpp
  tabjson.h
  table.cpp

- Implementing Discovery for the XML table type.
modified:
  domdoc.cpp
  domdoc.h
  ha_connect.cc
  libdoc.cpp
  plgxml.cpp
  plgxml.h
  reldef.cpp
  reldef.h
  tabxml.cpp
  tabxml.h

- Providing an error message when creating an ODBC table via discovery returns
  columns of more than one table.
modified:
  ha_connect.cc

- TableOptionStruct declaration moved from ha_connect.h to mycat.h
  To make it easier to use by other classes.
modified:
  ha_connect.cc
  ha_connect.h
  mycat.cc
  mycat.h
  reldef.cpp
  tabmysql.cpp
  taboccur.cpp
  tabpivot.cpp
  tabtbl.cpp
  tabutil.cpp
  tabxcl.cpp

storage/connect/table.cpp

@@ -587,6 +587,10 @@ CATCOL::CATCOL(PCOLDEF cdp, PTDB tdbp, int n)
 void CATCOL::ReadColumn(PGLOBAL g)
   {
   // Get the value of the Name or Description property
-  Value->SetValue_pvblk(Crp->Kdata, Tdbp->N);
+  if (Crp->Kdata)
+    Value->SetValue_pvblk(Crp->Kdata, Tdbp->N);
+  else
+    Value->Reset();
+
   } // end of ReadColumn