was not done correctly.
- Fix a bug causing add_field to generate a syntax error on DOUBLE columns
  with a 0 decimal value.
- Column can be undefined when Srcdef is specified.

modified:
  storage/connect/ha_connect.cc
  storage/connect/mycat.cc
  storage/connect/tabmysql.cpp
  storage/connect/tabutil.cpp
  storage/connect/tabutil.h