privType - (as int) Authorizer.SELECT_PRIV, Authorizer.UPDATE_PRIV, or Authorizer.REFERENCES_PRIV
forGrant - whether or not we are looking for grant priviledges
authorizationId - The user name
a ColPermsDescriptor or null if the user has no separate column
permissions of the specified type on the table. Note that the user may have been granted
permission on all the columns of the table (no column list), in which case this routine
will return null. You must also call getTablePermissions to see if the user has permission
on a set of columns.