Improve declare/fetch mode a little.

src/interfaces/odbc/connection.c

src/interfaces/odbc/connection.h

src/interfaces/odbc/convert.c

src/interfaces/odbc/dlg_specific.c

src/interfaces/odbc/dlg_specific.h

src/interfaces/odbc/execute.c

src/interfaces/odbc/psqlodbc.h

src/interfaces/odbc/psqlodbc.rc

src/interfaces/odbc/qresult.c

src/interfaces/odbc/resource.h

src/interfaces/odbc/results.c

src/interfaces/odbc/statement.c