DATA0TYPE.IC LINE 602

Deny the ALTER TABLE command if we are going to end up with too many
columns in the table.

Also lift the limit from the artificial 1000 (and remove the hard coded
magic number 1000), to the actual limit
of REC_MAX_N_FIELDS - DATA_N_SYS_COLS (1020) columns, add a new macro
REC_MAX_N_USER_FIELDS for that.

Approved by:	Marko, Joh (rb:1393)