Added MYSQL_TYPE_NULL as a dummy bind case for fetch buffers
Fix for offset based re-fetch using mysql_fetch_column
Misc cleanups for ODBC compatibility


include/mysql.h:
  Fix for offset based re-fetch using mysql_fetch_column
libmysql/libmysql.c:
  Added mysql_fetch_column function
  Added MYSQL_TYPE_NULL as a dummy bind case for fetch buffers
libmysql/libmysql.def:
  Updated new APIs